Incentive

Anger was always such a great incentive for him. Though combining it with his natural stubbornness wasn't always the best idea.
He didn't know anger until the douche called his father came to take him away from his grandmother. His father never cared for them until they were old enough to hold a dagger or any other weapon with which they could train. They were 6 when he turned up out of the blue. The asshole took them away from the only mother figure he ever had. He loved his grandmother dearly, Jacob and Evie didn't have a normal childhood with her but they were happy. But suddenly his dad shows up and moves them to the other side of Britain.
Evie had stars in her eyes the moment she saw father when she opened the door. Jacob's reaction was to cringe away the moment he saw those cold, hard eyes. Knowing from the start this would end in tears. Dragging him away the very next day from his beloved grandmother, who he only saw one more time in his life: at her funeral.

He knew from a very young age that his family wasn't normal. Of course not, the children he saw had a loving mother and father. He only knew a loving grandmother in a past. He knew his mother had died, but he learned about the details at the age of 12 during a shouting match with Ethan. Complications during child birth. The hate his father had for him was clear. Everything was alright when Evie was born. But their mother's body just wasn't prepared for the birth of twins. So everything went to shit when Jacob was born. Coming too soon after his sister, not giving their mother a chance to breathe. Ethan always blamed them but mostly Jacob. Which would explain the 6 year long gap and the life long struggle with his father. Never understanding why his father took him in in the first place. He could have easily just taken Evie. Not that Jacob would've ever allowed that.

During his teens he did everything to piss his father off. Somethings you can't forgive people. Like taking away a good and joyful life.
While his sister did everything daddy dearest asked of them. Jacob preferred to stay as far away from their place as possible. Preferring to hang around pubs to drink and gamble. Not that he needed the money but it was always such a blast beating people and seeing them put everything on the table just to try to win. But instead get heartbroken at the end of the night. Sometimes they beg to get their money back, sometimes they would just walk away defeated, and sometimes it would end in a brawl. Alcohol and anger weren't the best of combinations sometimes.
It took him by surprise one time, a lad who came to gamble to earn some money because he needed it desperately for one reason or another. Who didn't count on the experience of a 15 year old, seeing the kid as an easy target to get money from, being pretty wrong about that at the end of the night. The guy pulled a knife and was on him before Jacob could block it properly. That resulted in a scar the would mark his face for the rest of his life. Not that he complained his ragged eyebrow complemented his face in some way.
Now of course his father blew a casket when Jacob came home that night. "Blablabla you shouldn't have gone out in the first place… Blablabla you're an assassin in the making and you let a drunk cut you up… Blablabla what will the order think of me?" And of course everyone's favourite "why can't you be more like your sister?"

When his father got pleurisy he knew that it would be the end of him. They didn't start on good terms so why would it end in good terms? His final words were along the lines of "Your sister will become a great assassin, you though? I just hope you make something out of yourself and if you don't, don't take your sister down with you."
Ethan Frye ladies and gentleman. A dick towards his son the entirety of his life.
But what Ethan said that night did stay with Jacob for a long time. Making him angry in a new way, wanting to prove his father that he was worth more than he thought.

His anger made him want to prove things, but his stubbornness and hotheaded mentality caused him to make mistakes where he didn't want to. Which didn't help at all cause it made Evie angry. He didn't want the anger of his sister, he didn't want her to be disappointed in him like their father was. Because even though their father was a dick to him, Evie was often able to lighten up his mood.
Ever since they arrived in London they were at each other's throats. He knew that somewhere behind her dad-like façade she loved him and only wanted to protect him. But she had the same approach as their father had when he tried to make Jacob see reason the first couple of years.
The negativity when she said no to the rooks the first time. The disappointment during the bank fiasco. The pity after the Roth problem…
The only reason he was so connected with Roth for that little moment was because Roth was like the father he always wanted. Supportive of Jacob's manners and behavior. Thinking in the same way like he did. But of course everything had to go wrong. He should've known better "Don't let personal feelings compromise the mission." Ooh the irony since that sentence came from his should-be father figure. The story of Maxwell Roth ended in shock and disappointment more than anger.
Somewhere he understood his sister and he did try to be better for her. He loved her dearly and he would do everything that he could to protect her. If their father would have made them chose who would become the assassin between the two of them, he would've wanted it to be him. His sister was the better assassin in most ways but the life of an assassin isn't just books and pieces of Eden. No most of the time assassins had to kill and maim, or so he thought. Jacob would've done everything in his power to spare his sister from that. He always was better with the bloody part of being an assassin, Evie in the scholar part. In the end that would work out between those two. Since they were twins they were 2 separated parts of one being. Apart they were dangerous, but together they were lethal.

And Starrick soon learned that himself. All the anger in Jacob didn't beat Crawford with the Shroud. He was sure he was going to die. Starrick was draining him from his life, making it difficult to breathe. His incentive was probably the only thing that kept him alive until Evie approached. His anger and his stubbornness. Jacob wouldn't die in a forgotten cave somewhere beneath London. He would have a happy life in a safe London, Evie not too far from his side. Training the newest batch of assassins maybe getting some children with a spouse he loves and adores. Proving his father he was wrong to be disappointed in him. Jacob's life didn't flash before his eyes. No his possible future did.
After Evie made Starrick drop him. He gasps for air and channels all his pent up anger and frustration in avoiding the beams and working together with Evie. So that they can get that bloody shroud off of Starrick. They kill him the moment the golden miracle is removed from him.

He does prove his father wrong, and his life changes for the better. Every moment he lives no longer turns into a disappointment but into something good. Everything he hoped for in that cave with Starrick got true. Except for the moments where Evie was on the other side of the world with Greenie. But she would always return and end up helping training a new assassin or help with a new case. In the end his incentive became hope. But he never derailed from his stubborn nature.