One step further makes two steps back.
She told him "I love you" after an almost normal shift. It came out so naturally He wasn't even sure he understand well. He didn't say it back. Not that she was expecting anything, but deep down she felt a little disappointed. Not so long after that, he broke up with her in a parking lot.
He said "I love you" after an almost deadly shift. It came out so desperate she was sure he said it in the heat of the moment. She didn't say it back. But while he was half expecting this, he felt more than a little hope she would eventually give in . She never shown up at the Penny that night.
She came back from UC full. She was full of pride, cause she finished the mission and chased the bad guys; and she was full of hope, that for some reason Sam would've been waiting for her. What was it when she saw him kissing the other officer? Was it Jealousy? Rage? Disappointment? Regret? All of them?
It only took a couple of hours for her to fall from her cloud 9.
He heard her voice trough the phone after six months of silence. He felt relieved and proud, and all the regret he felt the past months was gone. For about a second. It came back worse than ever when he thought about the changes she will find once at the station, one of all Marlo. Just when he saw her at the station, after he kissed Marlo, he finally understood how he felt. Trapped.
She gave up her "Win back Sam plan" after a few weeks, when she felt the need to go on with her life, and let Sam live his. She felt sad, but free.
When she told him she was letting him go, was the second time (being the first the one when she held that stupid grenade), he thought he might lose her. It was the second time in his life he was really scared.
When he realized he was fooling himself and Marlo, was not so long after she started fooling herself and Nick.
When Kevin Ford shoot him, Sam's heart was not the only one who stopped .
It was her rambling in the bus, that made Sam see the girl he fall in love with.
How they made an entire year apart is a mistery, even for them. Truth is that neither of them is gonna give up this time. And it would have been easier for them to clean the air, if Sams heart didn't stop.