i have that! in fact the only things i've stuck with are my life (!) and being a mother to my son because i couldn't persuade myself that it would be alright not to.
Sometimes I think of my activities like "circling" around something ,homing in, so that although it can seem like you're all over the shop there's actually a common element in all the apparently unfinished projects, like when painting a big picture ( almost none of which i've ever finished to my satisfaction!! ), and move around all over; balancing, and counterchecking, and strengthening, in this corner , then another etc!!
That's when i'm feeling positive , haha, otherwise i feel like you; utterly p***** that so far have nothing to show for all these years of hopeful beginnings .
Well , that is except the story i tell myself about it all!!