It is better if those jobs are related so you can be less distracted and stop procrastinating. If they are not related, you probably should set a challenge to complete the second work.
N/A. So far I've never exactly been in said situation. But that said I am procrastinating my search for a better job somewhat bc, although low paying/not career/ not my passion, the job I have now has been fulfilling and a positive experience andstep forward.