please support the meaning of the above idiom with a clear usage
I will be glad if someone could throw light upon it's usage.
You've got a really important piece of work to hand in on Friday. You start Thursday night and just manage to get it done, instead of planning and starting your work a bit better- you cut it a bit fine there.
You've got a few coins left in your pocket on the day you get paid- you cut that a bit fine too- a person who budgeted would probably not be down to coins at that time of the month.