I have exactly the same problem. I started playing online turn based, and haven't gone back. 3 days per move allows you to really think about a move, use the analysis board, and be sure about a move before making it. Then it's about finding out how many games you need to have going at a time. I find 8 to 12 at once to be good. That way, I get home from work, get settled in, and have a few moves to make each evening. I don't have to sweat a clock at all. That being said, clocks are important things to learn how to manage for when you go to a tournament. At most tourneys though, you have much longer time controls than you will be seeing here. G45 or such is a fast one. I hate blitz, but I should play it to get used to the times when you get really low on time, say, before the first time situation is up at move 40, when the time control changes in some tournaments. Find people who will play unrated and play the crap out of blitz so you get a feel for it without wrecking your rating. Just a few suggestions or ideas......
Constant time trouble
If you are always in time trouble then you are thinking too much, about moves that are easy to find. Learn to bash out the easy moves (openings, forced moves, obvious captures and recaptures, pawn races etc.), concentrating your thoughts on the critical positions.
p.s. http://www.chess.com/chessmentor/view_course?id=221
Thanks for the help guys. I'll try to implement some of the advice.
Ok, first of all, ignore all the people telling you to move faster. That's not the way to good chess.
Your mistake is thinking that 15 minutes is a "longer" game. OTB tournaments are generally 60 minutes or longer. FIDE tournaments are generally 90 minutes +30 second increment or slower.
Chess is a game of thought, not banging out moves quickly. Dan Heisman is one of the best coaches/advice columnists for amateur players, and he recommends regularly playing slow games of 60 minutes or more in order to learn and improve. Some blitz along with it is useful, but playing slow games is essential if you want to get better.
GM Smirnov has a good video lesson about time trouble and time managing.
http://www.youtube.com/watch?v=uVqgKnv37m4
By the way, 15 minutes games are not long. They are quite fast games. Slower games mean at least 30-30 minutes, but usually much more.
For blitz games, and other fast games, here is another good video from GM smirnov: http://www.youtube.com/watch?v=R3DSqRvJbpA
15 | 10 is not anything close to a slow game. Everyone is in time trouble at that start of a 15 | 10 game :)
Go play a 90/30 game OTB and see if you have time trouble or not. Outside of the context of long standard time controls "time trouble" has no real meaning.
The art is to have 30 seconds back when your opponent resigns. If you want to play blitz and speed chess better, just play, and you will see at what points you will get better.
I once had a break from OTB chess, and then I got much better at blitz. When I came back to OTB chess, I began losing on time (or losing because of time trouble) in blitz again.
Practise is what I recommend. It worked out well for me, and I always end up in time trouble, but my opponents resign when I have 30 seconds back (or get mated when I have 5).
In blitz, the most important piece is the king. The second is the clock... Sacrifice your way to complicated attacking positions, where your opponent will either play inaccurate defence or lose on time.
I always seem to be in time trouble. Literally every game (even longer ones like 15|10) I'm well behind opponents on the clock and there's been a few games on here and chesscube where I've had a good or won lategame position but lost because I used up all my time to get there.
It's frustrating, any tips for improving my time management or is it just a matter of experience?