Passion is not something you lose or find. Instead it is something that you have to create every day. Don’t fall into the excuse that people use for quitting, “I lost my passion for X or Y.”
I believe that sometimes people over-romanticize the things that they do and when there are struggles and difficulties they then feel the grind and believe the task(s) have lost their luster. What needs to be remembered is that even in doing the thing you LOVE to do, there are probably tasks that make up 90-95% that you may dislike or even HATE to do but are necessary to do so you can do that thing you LOVE.
As the day to day grind becomes difficult, take pride in putting in the work. Do each task to the best of your abilities. Step back and reflect how each task leads you to be able to do what you really enjoy or to achieve the result you are really after.
It’s up to you to create the passion towards the end goal.