math is simple if you break it down into small, digestible parts.
there's a common military saying; "slow is steady, steady is fast, fast is good." basically, unless you can quickly give a close approximate to an exact answer, it's better to take your time and consider each step of a problem fully, separately, consecutively, before answering.
giving a proper answer is conditional upon understanding what is being asked and how to get where you need to go. when your mind is calm enough to see and consider steps individually (this just takes discipline; take the emotion out of the event and remember the patterns from solving similar problems in the past), you'll have no problem pinning down accurate answers without suffering 'brain freeze' -and with dutiful practice, you'll only get faster.
if a fast answer is preferred over an accurate one, memorize some recurring patterns (fast conversions, simplifications, geometric graphs and formulae, etc) and don't be afraid to round up or down to generate an easy, but close, answer. an engineer always looks to make things easier for himself and others, and rounding is ALWAYS justified if you can explain each step clearly. -at the very least, it gives you a close picture of where the true answer should lay.
a tip for remembering things; simply consider them VERY important -that is, of UTMOST importance. it's a simple step, but one which is often overlooked. -mnemonic tricks and mantras are also useful for memorizing basic patterns once the underlying principles -the rules and relationships governing your math- are laid down.
when creating useful memories, make sure you follow proper protocol: you must understand something before you can create a useful memory with it. make sure you understand relationships and completely get what is going on before you try to memorize patterns and complex tables; contrary to expectation, not every memory is essential, only those which lead to the right answer.
don't be afraid to take some time getting to the right answer. you only look dumb if you're hesitant AND you give a completely wrong answer. better to take some time and get an answer right, or take just a little less time and give a close answer fast. UNDERSTANDING is paramount -speed can be gained by rote practice, and is not your main contribution as an intelligent human being; a calculator can generate answers faster than any human, but a calculator can't answer why such information is important, or how to get there, or what information is important to get there. NEVER rush problem solving in math or science unless rounding is accepted, and always make sure you know how to take each step separately in getting to the final answer.
finally, good luck! perseverance and vigilance will be traits that will propel you to success!
PS: don't be afraid to ask for help (network) and get peer tutoring to understand specific relationships and get a clearer picture, or some fast mnemonic tricks. sometimes the hardest thing about math is knowing the right vocabulary to properly state a problem you 'know' how to solve (PSS: -you don't really know math until you can clearly explain it to a five year old! never forget, you must first understand something before you can remember it, and you must recall something before you can explain it. -get these steps out of order and your chances of screwing up increase by a factor of ten million (approx)).