Two people 'above' me have really kept me going with fish. One was a past Curator we only called "Tiger", the other is a shark researcher in the Gulf of Mexico.
However, truth be told, the biggest motivator for me have been staff who worked for me (both the paid and "free slave labor" interns). I'm serious. So much of my career has been dealing with people who used to love fish, but fell in love with money instead. I hate seeing things go that way.
Seeing a face that lights up when they feed and animal or clean a tank totally makes my day. Seeing people who start each day with a positive outlook with a goal of learning something and doing great things for the animals charged in their care is amazing. Knowing that I got to help teach someone learning the basics something new or show them a way to learn on their own means everything to me.
If nothing else, I hope my life is used to pass knowledge to the fishkeepers of tomorrow - so they in turn can pass on that, plus more to the generation to follow them.