Openings are not my main weakness. In most games I manage to get a decent play even against stronger opponents, as the start game of my last tournament shows.
But the tournament has also shown that I have a severe opening weakness: tactics. It has two main sources, as far as I can see now. Firstly, I am not yet tuned to tactics in the opening. My main goal is a fast positional development. Secondly, I try to move fast in the opening in order to gain time for the middle game and probably for the endgame.
A typical example of this weakness is my 3rd round swindle. I must confess that I saw the tactic immediately, but I also saw that it would involve a queen swap. Instead of looking deeper at it I decided quite quickly to play for mate and to keep queens on the board. This was easily refutated and I ended in a middlegame without queens and without tactics.
I managed to win at last, but only because I set a trap using a tactic. Against a stronger opponent this would not have worked.
The lesson to be learned from this game is: Stay tuned for tactics from the very first move! As soon as a possible tactic emerges, use some extra time on your clock.