A big thing is, as you sort of mention, knowing what your abilities are and using every tool at your disposal. It seems pretty obvious, I mean you wouldn't dps and never pop raging strikes in pve, right? PvP is a lot more situational so its easy to overthink, hesitate, and fall into the pattern of just not using stuff. Don't do that. Get in the habit of firing off everything you have when in doubt, and from there work on learning to optimize (when to hold back, what order to use stuff in, etc). Hopefully that makes sense xD For me it's made all the difference and the jobs I approached learning to play with that in mind I do much better on.

Knowing what tools your opponents have is important too. If its an option, getting PvP experience on other jobs, even if you don't plan on learning to play them well, goes a long ways.