The funny thing is, I've never heard of surgeons, accountants, cops, pilots, secretaries, engineers, having lack of motivation. You have a job, you clock in, do it the best you can, then go home.
However, Youtubers, artists, self published authors (especially on Kindle direct publishing), often complain about writer's block, artists block, lack of motivation, lack of inspiration.
The bottom line is, if this is your job, every day you clock in and do the work. Motivation is the work itself. It's your chosen endeavor. You do it.
If it's a hobby, and you don't like it anymore, then stop.
For me personally, motivation is the monthly rental bill and utility bills, a ballooning visa card statement, and bloody overpriced supermarket food. The alternative is a homeless shelter. f**k motivation, just do the job.