I find that thinking about the indidivual parts and organ systems inside my body is good motivation to look after it. There are a few specific thoughts I use which add to this. One is the idea of my body as belonging to God, and therefore something that should be looked after.

Another idea is to take this even further, and think of my physical body as a kind of "smartphone", or radio receiver, which was designed for me to invite God's Holy Spirit to reside in. And then I can use it to extend (or transmit) God's message, will, and purpose into the physical world — by the thoughts and actions I perform in my physical life on Earth.

Another idea is more basic and physical, and just to imagine the diffferent organ systems of my body working properly, and being healthy and in good condition.