Ok, I hate time pressure. Just the feeling that there is a clock puts me under pressure.

I noticed that I see far less just because I think about the clock ticking. (just had another of those "kicking yourself" moments with the TT)

I feel that my clock goes faster than the one of my opponent.

Anyone got an idea of what to do about this? This must stop. My head starts swirling once my time runs and I have trouble thinking straight.

I started correspondence games but feel that this does not help my calculation skills much since I can "analyze" everything on the board and go back and forth, something I could not do in an OTB game.

Your ability to play fast is a measure of your comfort and how much pattern-knowledge you have stored in your brain.  The former is just a statement of what kind of person you are ... the latter comes from months/years of deliberate practice of many slow games with the intention of identifying your mistakes and geting better.   It's not rocket science to claim that your "speed game" skills get better as your slow game skills get better.

The simple answer:  Play what's fun for you ... play longer time controls or time controls with increments so that you can gain time with each move. You'd encounter time-pressure moments far less.  As far as the nerves go, it only gets better with time.

Another more radical answer: Face your fear. Hate time pressure? Throw yourself into hours of blitz play until you shake off this feeling of confusion, hesitation or head-swirling.  Nerves only succeed in messing you up until the rest of your brain learns to compensate for them. So don't shield the problem ... attack it head on!

If there are no tactics, think about the principles.  Only take time if there is contact between pieces ;)

Thanks for all the helpful input. I don't do bullet or 3 minute blitz, only occasionally otb for fun. My usual timeframe in online games is 10 minutes or 15 with increment. In these games, there are two possibilities:

a) I feel like playing against a noob and just smash the opponent away for a bit, and then get stuck on the checkmate part, which I may manage to do - narrowly on time.

b) My opponent is good and controls the board fast. I make mistakes due to time pressure. As the game goes on, my opponents position will improve, and the time gap between us will increase in his/her favour.

So looking at your advice, it seems that I should go both ways:

Some slower games to improve my overall skills, wich then will help me in faster games. (I like that option more)

Some faster games to get used to time pressure. (I do that occasionally, since it is less enjoyable for me, unless I play OTB against some friend)

"How to keep my cool under time pressure"

Ice works great!

Try playing a couple blitz (5-10 minutes online, or 10 to 15 minutes OTB.) games. If you don't like quick moves, just play longer games with an increment. I happen to love it when my opponent and I are under serious time pressure.