Gunslingers are all about keeping them away from you because if they get to you its over.
Yah that's the tricky part...keeping them off you. I find at times it's easy, other times it's impossible! Even with CCs I can't generally get away fast enough, or I'm getting lightening in my back! I'm doing better in my early 20s then I was in my teens and I'm still having a blast. But yah Gunslinger can be a hard road....I hate how the 'cover' ability ****s with my hotbars, I've heard you can disable this but not sure were I find it. I'm also still fiddling with my hotbar set up for PvP, bot yet totally happy with it.
As for energy...it's the Smugglers bane I think, it takes practice to keep tabs on.