This is very beautiful! The song gives off a very calm feeling but also has passion in it as well as pulls on the heartstrings. I think the guitar you chose for this is perfect, and the other backing instruments too. If you want recommendations on guitar VSTs, Nexus doesn't really have a lot of good samples but Native Instrument's "Session Guitarist - Electric Sunburst Deluxe" and "Session Guitarist - Picked Acoustic" have a lot of realistic sounding guitar samples as well as a good handful of articulation/automation options. They are pretty pricy though so I suggest waiting till the next Komplete sale or something... but anyways thats just a suggestion because I really like the guitar you used for this anyways, it fits very nice!
As for the losing interest thing, sometimes it happens. I wouldn't focus too much on it because it can just make things seem more daunting... sometimes people temporarily lose motivation or interest, but it always comes back. This track really shows that you have talent and skill, so the problem is probably just a temporary block. Just play around with music more and you'll notice you're gonna start enjoying it again if you don't think of it too much! At least that's what I think haha
Anyways great work, keep it coming!