Willpower is exhaustive, enthusiasm is not. As long as you're excited about what it is you're after, there shouldn't be a need for willpower (or coffee).
I have campaigned for people and products through relying on - mostly - willpower. Until the campaigner in me, surprisingly, just stopped. After some inspection I realised, my willpower had dried up and there was nothing left to fuel the campaigner in me. Umpf.
So, what can I - or you for that matter - campaign for endlessly, that doesn't rely on willpower? It can help to look at life experiences that were formative and challenging, but not reliant on willpower.
I put a few down from 2008-2018 and suddenly saw what I can campaign for effortlessly: craftsmanship, playing with words, physical activity, mindful use of technology, yoga, food pioneers, going outdoors, talking to strangers, reading, eating plants, nature conservation, life-long learning - and this is just what's top of mind now.
Easy peasy, now it's your turn.