GMAT Strategy

Generally speaking, any bad habits you have in practice will get magnified during the stress of the exam. So if you're making a decent number of careless mistakes due to speed now, that number is likely to go up on the real test.

Keep an error log and write down not just what problems you get wrong but WHY you got them wrong. Then think about habits you can put in place to minimize those errors in future. If you are doing too much, or trying to remember too much, in your head, write stuff down. If you are trying to do two math steps at once, do them separately.

I tend to work too quickly on some question types too and I've instituted a rule for myself. I'm not allowed to spend less than a minute on a problem (less than 45 sec for SC). If I'm done in under a minute, I immediately do the problem again - all the way through and, if possible, using a different approach. This helps me to calm down and do the problem thoroughly the first time b/c I know I'm just going to have to do it again if I do it too quickly.