Certainly, if you can't manage your game, you can't play tournament golf. You continually have to ask yourself what club to play, where to aim it, whether to accept a safe par or to try to go for a birdie. You can't play every hole the same way. I never could.
You only hit a straight ball by accident. The ball is going to move right or left every time you hit it, so you had better make it go one way or the other.