This here.
I am a completionist, but there are times when I just don't enjoy the daily warframe grind anymore and just cold-turkey drop warframe all-together to move to one of my various other games to finish the last few achievements there or just play for fun.
The sense of achievement from completing a game (or achievement) is not to be underestimated, it can at times feel very rewarding. If however the journey becomes to much of a chore, take a break or bring down your velocity by playing less (of said game/content).
Also keep in mind, completing everything does not mean completing everything in the least possible amount of time. It is often much more enjoyable to take the long route and take your time to appreciate the content that is not the most efficient. There are some notorious grinds in warframe and my only tip for people stuck on those grinds they really don't like is to do 1 mission each day/week and thereby alleviate the sense of a never ending grind.