Dear Bill,

I'll take a stab at spendthrift and carelessness with money.

Let's say you're trying to be prudent, and you have this piggybank where you save your money for a rainy day. You try to be thrifty. But, being weak and careless, you spend what you saved. You'd be spending your thriftiness. You'd spend your thrift. You'd be a spendthrift.

Best that I can do,
Wordwonderer