KayLo!
Smarter than your average wabbit.
This is a bit misleading, and I disagree with Brawl being a game of reaction.it is soooo important that you react to your opponent rather than saying im gonna this and this and not try this. thats where your mindset is wrong. this is a game of reaction. if you react to opponent and take all his mistakes and punish the mistakes rather than try to land kill moves at innapropriate times you are gonna have a much easier time.
Yes, you should react to your opponent in some cases, but Brawl is a mix of reaction + prediction. Reacting all the time puts you on the proverbial back foot and can lead to overly defensive, slow gameplay. If you play solely on reaction, your playstyle will be easily overwhelmed by a good pressure game, and you'll also lack one yourself.
There's nothing wrong with keeping a game plan in the back of your mind..... just be flexible and able to adapt if you're not in the position to make it happen. Loose planning is fine; singlemindedness is what will get you in trouble.