For every phase of one's life, there has to be something bothering them. As one gets older, struggles simply pile up and there's no choice but to get better at dealing with them. Every year there'd be something others would impose on you, and you must accept it and move on from it, just for there to come up more expectations they would pressure you with. Those are simply the rules of growing up, after all.
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. He was suddenly the one responsible for defeating all of their enemies and securing a good future. Tajima expected him to stoically take the deaths of his mother and siblings, to never show weakness – simply put, to handle things which most adults couldn't.
Yet, he had done it. Somehow, he did.
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. Losing someone important no longer warranted a tight hug and a promise how everything would be fine; no. It brought even more pressure to develop his eye prowess and bring revenge.
Being robbed of his childhood left him unapproachable, jaded. It tired him out. 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 his firm decision not to get married.
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! To him, that was absolutely understandable – if Madara was born a female he would sew his legs together rather than bring 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.
Neither of them was too keen on 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 he wasn't of use to his 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 was 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 times and drag out the process. Izuna had, after all, agreed to let Tajima arrange everything.