Problems in need of generalizable solutions

What to do if you have some intrinsic motivation but not enough?

Sometimes I spontaneously feel like exercising.  Sometimes I don’t, but I prod myself a bit and am really glad I did.  Sometimes I prod myself a bit and am not glad I did.  Sometimes I didn’t want to be because of important but subconscious reasons, and doing the Healthy Thing makes me feel actively worse.  I worry that every time I push without getting a reward at the end I’m making myself ultimately worse off by eroding my intrinsic motivation.  That worry is itself a negative reinforcement that makes the outcome more likely.  If someone could send me a general solution that works for regular exercise, physical therapy exercise, cooking, eating well, cleaning, work, and extroverting I would super appreciate it.

What to do with an initial burst of enthusiasm?

I assume we’ve all had the experience of getting an initial burst of enthusiasm for something (e.g. clean all the things), only to overdo it and burn out.  Then we are sad, because our hopes have been dashed.  I assume many of us have learned from this to scale back our initial efforts and channel that enthusiasm into long term sustainable action, only to discover the enthusiasm has an expiration date either way, so now our hopes are dashed *and* we had the unpleasant feeling of bridling ourselves *and* we accomplished strictly less than we would have if we’d run with the initial enthusiasm.  Is there a third way that would let me accomplish all the things without every feeling burnt out or overextended several of the things with a minimal amount of overextension or artificially holding myself back?