Did you hear about the good old country boy nuclear physicist whose hobbies were huntin', shootin' and fission? Although I've never been an angler myself, I've always admired a dedicated fisherman's ability to become completely absorbed in the process of sitting on a riverbank watching a float. It's not really my thing, but what definitely is, is the glorious sensation of doing something which demands your complete and utter concentration for an extended period. You lose track of time. You forget everything else. You pack up your troubles in your old kitbag.
The splendidly named psychologist Mihaly Csikszentmihalyi calls this state of mind 'flow', and there's a huge amount to be said for it. So when were you last similarly absorbed? What were you doing at the time? And most importantly, when can you schedule some more of it?