Taking dead cold showers every morning will make you happier. Your body will make dynorphins, which make you feel uncomfortable. But inresponse to that it will also create new opioid receptors, which makes you sensitive to the next batch of endorphins, wherever they come from. The repeated act of choosing and resisting discomfort also increases your resistance to physiological stress. So taking cold showers every morning makes you (1) more receptive to good sensations, and (2) more resistant to negative ones.
Same rules for life. Pain is useful because it increases your sensitivity to pleasure and your ability to deal with subsequent pain. Both are important for a happy and fulfilled life.