Relaxation promotes hormonal balance. Hormones can settle into a natural state of equilibrium during relaxation without being over-run by flight or fight hormones. During meditation this effect is even greater because thoughts are no longer present (or at the least reduced) therefore hormonal stimulation is not influenced by thoughts either. Relaxation combined with meditation has the dual (jewel :-) ) affect of reducing external and internal stimuli for hormone production, therefore allowing your entire being to settle into a natural flow of balance and harmony, and take a much needed rest from the continual pressures of general life.
This is also why good sleep patterns are so important for well-being. Sleeping is the time, naturally designed by nature, for relaxation and restoration of the body. However, because dreaming and thoughts can still occur during sleep there is still the potential for unwarranted hormone stimulation, whereas during relaxation and meditation, performed in a fully aware present state, the stimulus is remarkably reduced. and the space to simply 'be' emerges.
So make a conscious effort to try to take some time out each day to fully relax. It's totally free and well worth it.
And if it's a struggle to unwind and relax there are natural ways to help: