Back to some basic issues ...
Most of the responses, including mine, have been from experienced divers discussing their issues. However, as TracyG noted, the original intent of this thread by tormat appeared to be from the perspective of a new diver. Thus, I'll also include a couple of new-diver issues: fussing too much with the buoyancy inflator and using too much arm movement underwater.
I dug back into the old archives (web archives, not here on D2D -- where there seems to be a permanent case of amnesia) to retrieve an old article I wrote on those two issues. It's at:
DSAO -- whether your diving issues are from few or many dives
I'm just here between dives unloading nitrogen, refilling tanks, and talking with buddies.
To echo what Jim says around the inflator. I can tell you, to the week, when I turned the corner on buoyancy. It was the week I spent in Grand Turk with an Air 2 inflator that had been incorrectly serviced in a way that caused air to exit my BC under pressure (diaphragm put in incorrectly so it wouldn't seal). This meant I was diving without the ability to keep my BC inflated. (And there was no rental BC available) I spent several dives tweaking my weights until I got to the point of being neutral at depth. (PLEASE understand, I do not recommend this...it was not very smart but, then again, neither am I.) From that day forward, I only put a few squirts of air in my BC for most dives (exception being the first dive or two when I switch more thermal protection and change my buoyancy profile). That one event removed my greatest issue. To resolve the swimming with your arms issue, the solution is much easier: get a big ass camera that requires to keep both hands on the handles at all times. (NO. I'm kidding. Well, it does work but don't get a big ass camera until you've got more experience.)
I'm afraid of sharks.
Nemo Me Impune Lacessit
Yes it was from a new diver perspective, but it was also ment to be a looking forward thread for me. Its a lot of fun for me (and i learn a ton as well) to hear all levels of "issues" that all divers have.
I know my biggest issue is just not diving enough!