When it comes to motivation, I think i just want to fc maps/songs that i liked.
As a Touhou fan, I really love maps with touhou songs, and there's one specific map that I want to be able to fc back then (
beatmapsets/656918#osu/1501711 <-the Lunatic diff specifically). But well, it's a 5* after all, back then I was only able to play 2*
I kept pushing myself, while setting goals that were more achievable that time, such as fcing (
beatmapsets/49852#osu/153515) hard diff. It wasn't easy... I have been stuck on 2* for 5-6 months during that period, I really thought it was my limit to play 2.7-2.8* back then.
But all the time I spent on 2* paid off, eventually I can fc 3*, one step closer to my initial goal. But soon there's the 4* barrier which made me deleted osu once. (You can even search for my first forum post if you want to know how hard i struggled). Still I made it... and you know the drill already so I won't drag any longer.
TL;DR: Play osu for songs/music that you like around your skill level. You don't have to play for improvements, as it would eventually comes to you instead. People improves at their own pace, but no matter who you are, patience is always the key >w<