Motivation like attention is a limited resource. We only have a small quantity of it each day (think of hit points in D&D). While most activities drain it, some replenish it. So what refiles your motivation HP?
I for instance am an introvert so to recharge I need to be alone or with one person like my wife (still working on that). I don’t go out a lot and don’t like to be in a place where people like to gather. If you’re an extrovert it’s exactly to opposite for you.
Motivation is only one of the stats you need to keep track of. Attention, discipline and motivation are the three major ones. Find out what recharges them and your results will skyrocket.