Ah, the story of my life... ^^;
In recent years I've been getting better at not taking all my ideas seriously, though. Like, if you can convince yourself that it's okay to have a neat idea and get excited about it, draw characters, write scripts, maybe even tell people about it...but not really commit to it in any substantial way at the end of the day, you will save yourself a lot of existential angst.
Simply taking the time to freely engage in creativity can be its own reward, especially when you already have ongoing projects. I have to admit, it does feel nice to have scripts I can just 'noodle' with, outside of the scripts that I'm actually expected to perfect, draw, and release to the public some time before they completely lose interest (and the whole endeavor becomes pointless...).
Besides, there are other options for backburner ideas...you can draw just one really fun page, or just a couple. =T You can format them into novels, and just draw character art. You can decide to ONLY draw character art, and just freely gush about the characters and their world to whoever will listen.
There are lots of smaller, less ambitious ways to share an idea and/or bring it to life, and I think they're still worthwhile despite their smallness. Better than locking it away and waiting for some magical day when working on 10 long-form comics at once will somehow actually be feasible...