Whether I'm a finisher or not depends partly on the medium and also the time and input involved.
I generally do finish my quilts - I put a lot of thought and time into the design, the subject has to be something that inspires me, I'm good at planning (the scientist in me!) and most of all I love the process of problem solving. So with all that investment I generally want to see it through. Sometimes quilts just don't take off , usually if I've done so much planning that there's little interest left ( as with my 'Weir' where the creative energy went into painting and Journal quilts leaving insufficient for the actual piece itself). Abandoning at an early stage is not the same as not finishing. Paintings are another matter!
With watercolours, where you can't correct, if something goes wrong then I start another one! Quick fresh paintings look better than laboured ones to my mind but there's always the risk of continuing to make the same mistakes! I'm afraid I've tended to apply the same approach to mixed media and acrylic paintings too but I'm getting better at persevering - my recent course at Slapton has helped a lot.
I usually paint directly in front of the subject or when working at home I surround myself with 'storyboards' of photos and drawings , so working only from sketches was quite scary to begin with. Initially I didn't gather enough information or was concentrating too much in making pleasing paintings of my sketches but my 'note-taking' has improved.
Working on this painting (need a name -orange rocks? ) was a revelation. Not having any photos (apart from the small screen of my camera) I used my sketches to block in the main shapes . Then I got stuck and would have abandoned it but setting sketches aside and with the tutors advice ( get rid of the green , change the direction of the rocks) worked into it more - the advantage of acrylics.
There's still a lot wrong with it but it marks a breakthrough in simplification and perserverance - I'm finally becoming a finisher of paintings too!