If you're going to be a black belt soon, I'd think you'd want to take a more serious approach to your strength training instead of a "time to time" approach. If weight training is too much of a hassle, consider bodyweight training. At the very minimum squats, sit-ups and push-ups. You can get more aggressive with bodyweight training as your strength improves, I'm also a big advocate of heavy bag training. You can build a lot of speed and power working the heavy bag. What ever you do, make it a routine instead of time to time. Good luck.