I dropped a customer around 8 years ago as she owed me for 5 cleans totalling €60 (I know, I know!)
I was cleaning her neighbour's windows recently, and she approached me and asked me to start cleaning hers again. On reminding her of her outstanding debt, she paid me €20 on the spot, and promised to settle the remainder next time I am around. I agree to restart once she is paid up. I'm not holding my breath, but it's a start.
John