Keep in mind how fast things pass by and are gone - those that are now, and those to come. Existence flows past us like a river; the "what" is in constant flux, the "why" has a thousand variations. Nothing is stable, not even what's right here. The infinity of past and future gapes before us - a chasm whose depths we cannot see.
I'm a big fan of working out on my own. I put my headphones on and I'm pretty good at self-motivating. At the end of the day, I enjoy it. Once I'm there and once I get going, I tend to love it, and I feel good.