I am looking for an idiomatic expression that expresses the idea of the negative consequences for having wasted your time or your money for instance, and now that you really need them you don't have enough.
An example may be a student who has wasted time and now they don't have enough to study for their examinations.
Best Answer
Consider the colloquial idiom fritter away.
Thus spake dictionary.com:
The lazy student frittered away his time, his parents' money, and his prospects for a prosperous future.