You're definitely going to want to do something with yourself. Starting to workout again would be a great idea! Maybe take up another hobby? Going to college would be good, but i can understand not wanting to spend so much money on something you're not sure about.
Even something simple as hanging out with friends more would help. Or if possible, you could try to get a girlfriend? Depression is much worse if you go through it alone, having someone like that by your side would be really helpful.
I don't really know much about you or your situation but you need to keep yourself occupied! How about every night before bed, you write down 10 things you want to achieve tomorrow. They don't need to be big things, just little ones. E.g, Go a walk, Update my PPR, Message 3 old friends, clean out the attic, ect ect
Or you could try looking forward towards the future. Just think in 10 years you'll be living in a house somewhere with your wife & you'll have a child and a pet dog named Scruffy! You'll sit at the table every morning and eat breakfast together, then all go off to work/school. You'll get home and relax with some tv, maybe help your child out with their homework, walk the dog and then fall asleep in bed with the woman you love. That's not impossible, theres even a lot of people on here who are already living that.
It may not sound really exciting, but isn't it worth living for?