Keep your cool in combat. It's a simple rule that applies strongly in the real world. The fighter who can maintain composure and think clearly has an advantage over one who loses control, gets flustered, and starts getting sloppy.
But not in a roleplaying game! Fighting is all about brute strength and unconstrained rage! Intelligence is well-known to be the time-honoured dump stat for fighters. And if you manage to go completely stark-raving Berserk, it gives you bonuses in combat!
This is all well and good, if you want to play it that way. The truly good thing is that the rules of most games support that sort of combat behaviour, so you don't need to justify the suspension-of-disbelief-breaking unreality of it all. But if you do want to play it cool and be a level-headed combat monster instead, you can justify that as well, on the grounds of reality! In fact, if you're not getting combat bonuses off your GM, no matter what style of combat you use, you're just not trying hard enough.
Obi-Wan: I'm terribly afraid I'm going to have to take the Peace Moon plans back now.
Count Dookû: Certainement, on condition you expose zem to ze Senate.
Obi-Wan: We promised to give them back to Palpatine. And I always uphold my promises. Hand them over.
Count Dookû: So now Ah 'ave to defend mahself against you as well.
Count Dookû: Zhust do not come running to moi when ze Chancellor turns on you.
Anakin: Don't listen to his Sith lies!
Count Dookû: If zere is a Sith anywhere, it is Palpatine!
Count Dookû: <sigh> From ze impetuous young squire, to ze crazy old coot 'ose 'ead is all full of fanatical ideals.
Count Dookû: Your mother was a womp rat and your father smells of sweesonberries!
Obi-Wan: Your taunting won't work on me, Dookû. I'm completely in control.
Count Dookû: Oh well, worth ze try.