Kagebunshin as new ninjutsu confirmed for 5.0 :P
In all seriousness though Kaiva, yes I do believe you can overwhelm yourself if you try pushing too hard. Improvement comes at a different pace for all of us. From what I've been able to tell, seems to me like you've been trying out many different jobs trying to find your niche. That's not bad by any means! But it can also be time consuming as well to learn and improve upon so many different things. If my memory hasn't failed me (and correct me if I'm wrong), I seem to recall that across two different toons you've done raid content as an AST, some kind of tank (PLD I believe?), SMN, DRG I think, and now it seems MNK and NIN as well? I might have missed one or two, but either way that seems like it would be a lot to try to learn and improve enough to be raid ready. That you've been able to do savage content using so many different jobs is already fairly impressive in my book, and also it must have taken a decent effort to even gear them all up enough. It took me months to get to where I'm at with just SMN (which can still use work), and it would probably take me more time if I ever wanted to try savage content again with my RDM even though I'd like to think I understand the job well enough. I certainly couldn't hope to try it out with a different role from DPS altogether anytime soon, as I don't have the best handle on WHM yet, haven't even really bothered with my SCH, and barely even scratched the surface on tanking and aren't even leveled up enough with anything to try raid tanking, let alone being decent at it.
I guess what I'm trying to say is that once you've settled into a job you feel works best for you in high-end content, you'll likely be able to develop your skills with that job and see more improvement. Take your time, see what works out. I know it probably seems like a cop-out to say to keep practicing and do your research on rotations, but they're pretty tried and true methods all the same. Also don't try to spread yourself too thin either and, as I'm sure you're tired of hearing by now, don't be too harsh on yourself if you're not yet at the level you want to be at. Like others said, setting goals can help. It's good to have a long-term goal, but it's also just as important, if not more so, to set smaller short-term goals to gradually work through over time, even if it's just upgrading a piece of gear during the week or beating a SSS dummy. Every little bit is a step closer to being where you want to be. And keep working on those EX and savage fights. The more familiarity you get with them, the easier things will get for you. It's understandable to get frustrated sometimes, and I know how hard it can be for you not to be critical of yourself. But I still think you have potential as long as you strive to do well and learn to enjoy the small victories on the way to your ultimate goals. Use your mistakes as learning opportunities, but try not to dwell on them either. Learn from the past, work for the future, but don't ignore what you have in the present either, and you'll be in good shape.