Do you typically bill by the hour and only invoice after completing work? I found this problem common when I did that. Once I switched to (primarily) fixed fee arrangements and, in particular, to requiring a substantial payment upfront (half or in entirety), this problem went 80% away (which is good enough for most intents and purposes).
I wrote a bit about how I did this here: https://medium.com/solo-consulting-insights/how-to-get-your-consulting-fee-upfront-621d220ec779
I’d be curious your thoughts about applying it to your freelancing practice.