For every phase of one's life, there has to be something bothering them. It's not in vain that people say "life is a struggle". Literally, every year there is something that others impose on you, and you must accept it and move on from it, just for there to come up more expectations they will pressure you with.
Madara was, of course, no different. As a child, since he stood out among other children in the clan – even among adult shinobi – they shoved tons of expectations on him. Tajima expected him to stoically take the deaths of his siblings, to never show weakness; simply put, to handle things which most grown up's couldn't.
When he got slightly older, it was all about Sharingan. He had awakened it much earlier, but everyone waited around for him to unlock this or that power. Whenever an Uchiha dies, he felt like nobody even looks at the corpse, everyone just stares at his fucking eyes to see if there will be any changes.
Not being allowed to have a childhood left a huge impact on him. It tired him out, made him slightly cold and unapproachable. But there was no way he could have changed that; he was, after all, only a child, and he had to do as his elders bid him.
Since he had grown up to be a young man, however, he promised himself he would not let others make him live his life by their wishes. That's where most disputes with his father came from, actually – the latest one being marriage.
Shockingly, sending barely trained children to battle resulted in a serious drop in birthrate of the clan. Not only did so many, potentially great shinobi, die prematurely, but people held back from producing children, some hid their children away! That was absolutely understandable – if Madara was born a female he would sew his legs together rather than bringing forth children that someone would so easily send to die.
Tajima insisted that he or Izuna – preferably both, since they were now old enough – take wives and start reproducing as soon as possible. They were told to pick a girl from the clan, or one would be arranged for them.
They both hated the idea. There was hardly time for rest and basic needs, much less for romance. So, while Madara endured his father's reprehension and being told how 'he never wants to think of the clan', Izuna didn't prove to be as strong-willed in this matter. Soon enough, he gave in, and was arranged to marry.
Uchiha Mego is her name. That's all they knew at the moment. Father decided that Izuna would get to see the bride only in a fortnight, at the wedding. He wouldn't have his son change his mind a dozen of times and drag out the process. Izuna had, after all, agreed to let Tajima arrange everything.