Inadequate time management almost always leads to some form of stress. Conversely, stress of any kind often leads to improper time management as well.
Trying to do too much in too small a timeframe is one of the most common types of stress. It is very easy to get caught up in the "I must do this! I must do this!" mindset. When in such a state, simple physical relaxation is not enough - you have to learn to lower your expectations and 'stretch out' your sense of time again. (Miraculously, you can get more things done if you are focused but not in a hurry.)
Even if you start out with one kind of stress that doesn't involve time (for example an emotional issue), one type of stress leads to another, and it multiplies until all your time is taken up by stressing over something.
The best way to deal with time related stress is a kind of 'emotional time management': try to suspend yourself in a timeless state of mind. When expressed in words, such a state is a bit of a paradox - you have all eternity, yet the only moment that matters is this one you are in right now. Practice makes perfect - try it!