I've found periods where I've gone to the gym have been characterized by improvements elsewhere too. But then either the novelty of going to the gym wore off or life circumstances changed (move house / workplace etc) and gym stopped. That's gotten me like 3 times now.

Come to think of it in uni when I first started going to the gym coincides with the semester I actually got a D+ and a D- because I got distracted by going to the gym and chasing girls.

Mixed bag. Keen to start up again though, I do think it's helped when I can manage.