As you may have guessed, the best solution is probably to slow down. By committing more time on each move, you'll be forced to play fewer games due to time constraints. Of course the main problem here is that you won't have to spend too much time in the opening that you're familiar with. I think the problem you might be having is that you go quickly in the opening and start a lot of games, but when you need to slow down during the middle game, you can't due to the number of ongoing games and you get overwhelmed.
However, I don't think 30 is necessarily too much. What's the average time control for each of them?
Most of the people I play always take their time, and I end up starting to start more games, no matter how much I try to stop myself. I took a sample of several top online chess players and see that they, on average, have around 15 games going, when I have 30. At one point it had become 200, but gradually lowered to around 25. Not like live chess, where you are resricted on time and can't log off for 1 hour then log in. I was thinking of specifying in my seek someone who is a fast mover. My addiction to starting chess games has become too strong. Can anyone give me a solution?