Starter question for 10: You have a critical match coming up, know you will be playing a very strong opponent and have half-a-day free at some point before the game. Do you...
a) Go out drinking and cavorting with your pals on your time off, ending up in a casino at 4am without your shirt or the taxi fare home? Or,
b) Lie in bed for a few extra hours dreaming of winning a brilliant game and being showered with gold coins by the enthralled masses around your board? Or,
c) prepare as thoroughly as time allows so that come 'kick-off' time you have a good idea of what you intend playing and why?
If you answered a) you are me 20 years ago! I once partied 'til 7am, got woken up at 7-30am, poured into a car (drunk as the proverbial skunk) and ended up beating an IM and drawing with a GM that day! Fun, but sadly those days are long gone.
Perhaps you answered b) ? Fine, but don't come crying to me when you lose horribly - apart from which there are infinitely more interesting things to dream about!
Anyway, I mostly answer c) these days myself, and so should you if you are taking your chess seriously. I have found that my best games are those in which I have prepared myself both theoretically and practically for the game in front of me, and the following game is a good example of how this helps.