- the fabric is not washed
- you don't have enough thread
- you don't have the right size pattern
- your house is too messy to sew in.
Well, I cleaned up the bench that I cut off. Then I realise that I don't have the size that I want. So I draft up that size, plus some others. Right, then the fabric is not washed. Okay, that won't be done today seeing as there is a pile of other stuff in the queue (including all the towels etc that were used to mop up the laundry after an accident involving trying to recycle water in one way or another - don't ask). So you pick out some washed fabric, with a pattern that you have already and, yeah, probably not enough thread there.
Okay, not to worry, as I am topstitching in a different colour and the skirt is a differnt colour with which I have plenty of thread.