As a musician I commend your decision to putit on the shelf. My favorite sound is an accordion being thrown in a dumpster landing on a banjo and a ukulele.

I'm trying to learn Spanish via an app.. I'm bored of it, it's been a week or so

I love to learn. I'm even learning a new position at work. Can't say I've ever gone to the expense to get something then given it up. But, I've spent most of my life financially struggling so, anything that costs money is highly treasured.

Yeah because you're doing it backwards. Don't get all the stuff. You're getting ahead of yourself which triggers kind of an internal reward mechanism that makes you feel like you've already accomplished the goal.

What I do is instead of new years resolutions I pick a skill that I try to master. And I stick with it and obsess over it for a year, or more until I think I'm proficient enough to get results with it. The ability to get those results consistently is the reward I'm looking for. So I try not to talk about the new skill I'm working on much either since that also can have a similar effect as making you feel like you've already mastered it.

Playing guitar, but it comes and goes. I think I need mote patience if I want to play

I find that that happens more with things that have a steep learning curve.

Yup. 3D modeling and trying to learn Zbrush. I'm still trying to learn it but lost interest.

I think most people have experienced that. A lot of things seem like more fun than they actually are, and when it comes down to actually doing, it way too often seems more like work than fun.

Cannot think of any occasion, most of the time my enthusiasm grows the more I learn about something.

yes, often. No matter what I choose to study these days, the initial elements of which ever course are always legalities, health safety etc.

A few come to mind: Asian cooking, baking bread, woodworking & lathe work, astronomy. Don't be hard on yourself; who knows when the inspiration will come back. I have made the mistake of selling gear and equipment, only to regret it a year or two later.

What I thought were passing interests still interest me from time to time, so when the mood strikes, I go and do [fill in the blank] for hours on end. I guess they're more occasional hobbies. I have my steady ones: guitar, flying drones when weather permits, camping, photography, making beer & wine.

Wine making. I bought all the gear, then remembered I don't like wine.

Often. I have come to understand that anticipation can be as rewarding as the actual goal. I like to build and invent things and have had times where, when I finished, it did not turn out as I had hoped. The letdown was, at the end, not during.

Yup ... at separate times, needlepoint, then eventually crocheting. Both turned out to be duds. I'm just not cut out for either of them. Ha.

Sorry but that's funny to me.
My sister bought a Uke about a year ago, she plays it for hours every day and she can't play that song either.
Don't beat yourself up about it.

maybe you need a different song