‘I think the best thing to do when you feel like you’ve ‘painted yourself into a corner’, is to stop! You may think that by squeezing out fresh paint onto the clean spots of your messy palette, you will break the spell and revive the Muse, but unfortunately this option rarely works.

However, take care not to completely stop your art practice and thereby indulge yourself in frivolous behavior. 
Work on your website, plan an open studio, set a date and invite 3 or 4 collectors and art lovers. Tidy a chaotic corner of your studio, read your notes or/and clean your brushes. 
Please, just don’t ever stop doing art-related tasks.  This impasse concerning a specific piece, could last a few days, months or even years! Start something new, try another neglected medium, study all the found objects lining your window sill, make some quick sketches, as long as you ACT and DO something, anything! you will be making remarkable progress.’