I used to do it all the time early in my IM days. Years later I found 2 e-books that were halfway done, and forced myself to finish them and sold several thousand dollars worth of each! If I didn't sit down and combed through my old stuff, I'd be leaving this money on the table.
It surely isn't fun to finish some old boring project. But hopping from one thing to the next "latest and greatest" surely won't make you money.
How many abandoned projects do you have? It's time to re-evaluate them - there might be *gold* sitting right there in your "Documents" folder!