The Speedway League School/Freedom from your Brain Children
If you're a creative person, you just know it. Rarely do creative people need to be reminded that they think of things that others wouldn't, that they are easily distractable, and they need to learn to focus on fewer things. What they usually only learn through years of toil is how to deal with the parts of themselves that others rarely see; their ideas. It's been some years since I've started to treat thoughts as independent living things, and I think the classification has some merit. In moments of communication or inspiration they are born, they feed on our attention, they spread and multiply, they fuse with other ideas and evolve, and they can pass from host thinker to host thinker quite easily. I'm really liking the term "Brain Child" because it so accurately describes the relationship that any serious creator has with their ideas. They are the apples of their eye, which they love, and they put their time and love and energy into them to nurture and see them grow. Some succeed, some fail, but all have at least some share of the love and attention of the thinker who thought them. By this same token, they can be quite draining, and it takes most creators time to learn the best way to interact with their creations so that the life of both is optimized.
Look at them as tools in your toolbox rather than screaming babies!
It's impossible to nurture every idea equally. A small number of significant ideas can often be enough to occupy entire careers, and creators are usually plagued with far more ideas than they can possibly bring into full life. This typically depresses people who spend any amount of thinking of all the things that 'could be.' It is indeed exhausting to think this way, and that's precisely why you shouldn't do it. It's impossible. Give up now.
What you can actually do to is at least keep records (video snippets, notebooks, etc.) of the ideas that really inspire you. In a way it's good to work on ideas when you first get inspired, but even as a full time artist I still can't even keep up with the ideas I had 10 years ago much less all the new ones I get. The funny thing is that my most freeing realization came out of the failure of an album I did. I spent hundreds of hours writing and recording an album which failed in crowdfunding utterly and essentially generated nothing but a lot of work for me. That's a slight exaggeration, in that I did like the songs and I grew as a writer by making them. Still I would have preferred to have gotten some kind of return from people for all the work I put it. So I realized when I went back to my notebook, I could try to put together a better portfolio of songs that would be more successful while still being artistically satisfying. Then I realized...most of the ideas in my notebook weren't particularly fit for that. I had written what I wanted to, but it might not have been what I needed. What I needed was so much more specific than most of the chicken scratch I had once thought was the seeds of genius! In short, the affection I bore for my own ideas would not necessarily be shared by the world and that it wasn't at all in the interest of my career to just develop every idea I had. Although it seems cold at first, I realized over time that it captivates a more adult relationship with your creations. They can't all get as much attention as they could possibly benefit from, but neither would they all have a place in the world even if they could. It lets me think of my ideas as less of screaming babies that must be fed, and more as fond flashes of inspiration that will be there for me should I ever return for them.
The essence of that problem comes down to this; do you write just for yourself or do you want your music to affect others? If the answer is the former, then you should ask yourself what part of the process you enjoy the most? If it's the moment if inspiration, then that's like saying you got married because you wanted the wedding and gave no thought to the decades of committment that come thereafter. If you enjoy the process of growing and exploring the ideas, then one idea will often last you a long time and there's still no need to develop every single one as long as you have at least one idea that inspires you at any given time. If what you love most is having all your ideas finished, then good like trying to keep pace with your sporadic inspiration, though I can tell you I don't think I have ever met an artist who has. If on the final hand you do in fact write for other people, then realize that the world will not love every song you write equally no matter what you do. Even in the case that you want to give the world as much of yourself as you can, you're still better off picking and choosing carefully where to put your love in your songwriting since whatever you do put out there is going to need a lot of love.
You are not your creations
Another common thought is that if you write a bad song that you are a bad writer or bad person. Again, I think of songs as ideas as separate entities, and I always find it helps. Identifying with your songs doesn't serve many purposes other than to incapacitate you when you need to do what's best for the song. Sometimes songs come out bad. You can either pout about it or you can rewrite it. You can rewrite it 50 times. It's often good to put lots of work into one song just to see how far you can take it. Still if you feel every rewrite is a blow to your ego or an admission of failure, you'll never get through it. Give some space between you and what you create. It is only a reflection of your thoughts, not who you are or what you are at the deepest levels.