I need my shower in the morning, or my day isn't right. Sometimes, a shower to wash off the day is, indeed, refreshing, rejuvenating (and welcomed by my household, lol!). I do like tepid showers, not necessarily cold, unless it's very hot out; and I do like my ice bath after a long run. You'd probably not think of that as very relaxing, but it's certainly therapeutic.
Yes, I do think a shower can improve your mood.