When you hookup fMRI you can actually use live feedback to train motivation: https://www.ncbi.nlm.nih.gov/m/pubmed/30047755/
Personally, I don’t accept the conventional definition of motivation. It’s circular and self-refuting. There are actors and there are talkers. No one is always “motivated.” We build habits. We generate skills in accountability, reliability, and sense of duty.
Even the once-great hope that we could pin “motivation” or aggression on a genetic determinant has been thrown in the ash heap of intriguing but misleading scientific tropes: https://blogs.scientificamerican.com/…/code-rage-the-warri…/. That was quaint.
The more productive question to ask is what WILL someone do. This relegates motivation to the space it should’ve long ago occupied: cute jargon. People, therefore, aren’t faced with a seemingly-impossible task of magically increasing “motivation” (whatever that is anyway). Instead, we accept their current level of drive and difficulties, and use intelligent strategy to meet people where they are.
It could be 5 minutes. It could be one nutritional change. It could be daily gratitude journaling. All that matters is the person WILL do it. No try. No attempt. No sounds good. No exciting 6 week program. Just real and honest steps.
And to boot, keep in mind that neuroscience is showing we can train this motivation thing if you really want that too.