(Over)Stretching Your Comfort Zone
Be sure BEFORE you sign for a project whether you can deliver or not. It is probably the worst nightmare and questioning your professionalism if you cancel the work on a project in the middle because you realize that you cannot deliver what is requested from you even though you could see this coming.
So if you get asked to do a gig that is outside of your comfort zone, make sure whether this is still something that you can pull of or not. If you agree to do a deal and in the middle figure out that you cannot deliver, unless there is a plausible other reason to cancel the project, you need to pull it through at all costs even if that means that you need to hire external forces and your income for the projects melts to practically zero.
But abandoning a customer who has a deadline to meet as well and didn’t do anything wrong in the middle of a project is close to a personal professional suicide and has a very high chance of derailing your career.