This has been going on with me in periods for the last 10 years.
The last gig I did as a keyboardplayer was 2001, after a period where I actually from the start had quit playing but was headhunted by a really cool band so I joined them at a hobby basis around 1998 after more or less giving up playing 1996 due to exactly this "fallin out of love" thing.
The band was great and we had a fantastic time together through those 3 years, but then we all moved in different directions in the world and had to split up the band, though all the guys are today some of my best friends, though none of us really even bother thinking about playing together again, but you never know...
Since then I have been composing and producing a bit, but mostly been playing around with technique stuff and computer recording just for the **** of it.
I started playing the bass in jan/feb this year, initially to use the bass for my recordings (see link in my signature for more info), but then pretty fast it turned out a new hobby and now I play a lil every day, as well as I play around with pedals, sound, and actually also started to do some setup and easy luthier works (defret, fret-levelling, electronics) the last months too.
I am not "on fire" when playing and learning new stuff on the bass, but I enjoy it, and it has a nice lil place now in my heart, it seems like a hobby that is here to stay and maybe in a year or so I'll hook up with a real drummer and jam, for the first time in my life, on bass!!
The spark comes and goes m8, let it be for a while and do other stuff, and one day it'll strike you again, at least that's my experience of this.
D.Don