Yeah, second this. My physical therapist after my stroke recommended doing thirty pushups and thirty situps every day... which when I started would take most of the day and leave me wiped out (because, hey, stroke) and after about six months of PT became something I knocked off in the morning before going to work, but I regretted giving up the habit (and have recently picked it back up).
This September I'll start college aiming for a computer science degree, and I want to use the summer for self-improvement. I'm very uncertain about what skills I should try to learn, though, and recommendations would help.