Yes...I go through the same thing, which is why I have lots of projects going at once. They are all in different stages. So I can switch tasks if needed (quilting, piecing, applique, etc...) . I find that BOM's and other groups like that keep me inspired because there is always something new and fun to try and then to share.
I also realized at some point that I do have to give myself permission to punt. I don't HAVE to finish everything. If the blocks aren't going the right way..they can become orphans for another project and I can reclaim the fabric. I've even given mostly done projects away that someone else finished with wonderful results. (I did that with a one-block wonder earlier this year. The idea was great, and I got the triangles sewn into the threesies, but a seized up when it came to sewing those rows together. Ugh. The person I gave it to make a charity quilt and was THRILLED!)