The thing about relaxing is you should relax unneeded joints and if you using every joint then some of them have all ready have contracted or extended, etc all the way. So there is no point in using them unless for some reason you have to do it for the move your doing. Also I've learned relaxing at least for me makes it so i have a lot more options in a fight. That could be just me though.
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And one more thing relaxing has saved me from being dmed a lot, and it helps get some of the moves timing perfect so it connect with full power. Also if you need to see it look at Swex's replays he does a lot of really good relax techniques.

ok thanks i will be relaxing more often now

Another 1: in aikido-like mods, try to screw up your opponents movement (ghost) as much as possible. Example: a single hit or kick can be unexpected enough for your opponent to screw up and DQ.

Facts that noobs don't know:

Contracted wrist makes elbow faster.
Relaxed knee (usually) makes kicks more powerful.

Thanks for the tips i think ill consider some of them.