I've been at a similar place for quite some time now. When I play my best I'm good enough to win. When I don't, I'm bad enough to do rather poorly. If i'm tilted, its only worse.

The problem for me was just my own emotional/physical state. I put in long hours at my job and spend a lot of time traveling. Often I found myself playing poker when I was tired, exhausted and not concentrating on the game.

You are on the right track, examining your psychology while you are playing. Recently, I've come to grips with my entertainment/profit percentage. While I take poker Very serious and show profit at lower stakes, poker is still very much entertainment for me. Further because of my limited time to put into studying, etc, I have to be at 100 focus, concentration to play against better opponents online ( which I don't operate at very often) As a result, I keep poker 'new' at the lower stakes by learning new games. I find that playing a new game Forces me to focus.

Sorry if I took a tangent too much to my only world, but just trying to relate what I've found ...