That's so true PDM - and medical studies have proven that smiling actually affects your brain! That is, if you smile even if you're not happy, you start to feel better. If you frown even if you're happy, you start to feel worse. So, odd as it might sound, your body is affected by whether you force yourself to smile or frown.
It's worth it to smile while you shower!
Of course it's even better if you play fun music to get you to smile naturally

Figure out what colors appeal to you personally, and use those colors in your daily workspace / play space. Even small splashes of color can make a big difference.