I struggle with this one a lot. As I've improved, I've gradually starting doing more, like going for a walk outside most days, reading more, spending more time with my girlfriend, or watching more TV.

My baseline approach is:

- More than minimal symptoms? Rest (which could include sleeping, lying down, taking a bath, meditating, light reading with breaks, very brief conversations, etc)

- No symptoms, or minimal symptoms: OK to engage in activities, as long as I don't increase my activity level (ie, compared to previous outings/tasks) by more than, say, 5-10% unless absolutely necessary

In other words, I'm trying to take things incrementally and super-slow. I don't always hew to this approach - sometimes I just need a bit of fresh air, or human contact - but this is what seems to work best. When I'm in rest mode, I try to remind myself of my long-term goal (full recovery), and that rest is in large part what has got me this far.