Just go outside and enjoy nature or try doing sports (I interpreted going out in context with people) After riding my bike or running a bit, I often feel like I've accomplished something, even if it's just the feeling of exhaustion. Depending on your situation, getting a dog might be a good idea, since it's a living being that depends on you and forces you to take a walk from time to time.
As
>>2 already pointed out, study or train something. Especially once education leaves your daily routine, I think it's a good idea to start learning a language as a hobby. Of course you could also try art or literature or anything that interests you.