Any suggestions aside from the generic comments that seem so obvious but are almost impossible for a competitive person to do consistently that I could try to become more relaxed and consistent in my game?
you're not the only one that suffers during the early parts of rounds (well, it either starts strong and deteriorates or starts weak and takes forever to get in gear).
from the sound of things you would benefit from 10-20 warm-up drives in a field before playing a round. this will get the sallied drives out of your system and be enough throws to realize if you try to kill stuff out of the gate your timing will be hosed. you just have to make sure the throws have no consequence, so that all of the early round bs gets filtered out early.
the other thing you can always do is form "game plans" for holes and then you don't really think about things except for on a shot by shot basis. e.g. hole 1 "gentle hyzer, 5-10' inside that tree on the right." then it becomes a simple game of execution. i've seen many rounds from other players deteriorate because they try stupid crap on holes because they were "feeling it."