Difficult to fight against feelings. But you should try something very easy to prove at least one part of your theory wrong: results are not pre-determined. At least the ones where one manager is in. Choose a game where you are huge favourite, start your best 11 and join at half-time. The chances are you will be leading. Then, switch to a silly tactic (no GK, players out of position, etc..). And you'll see if changes do not have an impact. You may easily go from 4-0 to 4-6. Did it several times when I was tanking. Sure, the changes have a more subtle impact in a real game against a serious opposition. In a way, it's good. Otherwise it would mean that whatever mistake you did at the beginning of the game could be solved eventually at your oppo's expenses. Sometimes I could not recover from my earlier mistakes. Sometimes, if I lead 2 or 3-0, I try to anticipate what the other is gonna do. And you may imagine it works the other way round as well, making your changes useless. And sometimes, it's just about luck, like in real life.