An engine isn't self-sufficient. It runs on fuel it doesn't produce, it seizes without oil, and anyone who has driven a car into the ground knows that skipping the small maintenance is what ends it. If you are going to be the engine, take the metaphor the whole way. Sleep is oil. So is the friend you talk to on Sunday.
The heroic reading — never stop, run flat out — is how people end up abandoning things they loved at month eighteen.
Ask what your engine hasn't had lately, and give it that first.