Workout is not the only way to let go of stress, since it is not the only exercise that give you endorphin. There is actually one way that is a lot better from this aspect, since it makes you happy before, during and after you have finished doing it. And it is sex.
First of all, it gives you a way to exercise. By moving your muscles, the tension and spasms will lighten up or if you are lucky, they might disappear completely. This is also part of the reason why a workout makes you happy, as well. The other reason is that it gives you a feeling that you are able to overcome any problems and you can achieve whatever you want. So, if you think about it, you have a goal in sex, as well, and this is orgasm. If both of you reach the climax, it gives you both a feeling of success and achievement, so you will not only be satisfied because of the hormones released during climax, but also because you get to feel like a winner, as well.
And since stress is usually caused by ignorance and too many duties without appreciation, the intimacy between two partners adds the essential extra to the already great stress release. And now that you know why it is the best activity during hard times, you should start doing it every day to have a happier and more satisfied life that you deserve. If you are single find a fuck buddy, or if you are in a relationship, then spice up your nights!