Idiom request for wasting time or money

A person who makes bad decisions now and will have to pay for them later can be said to have mortgaged their future. A single word for this would be to squander time or money.

Consider the colloquial idiom fritter away.

Thus spake dictionary.com:

verb (used with object) 1. to squander or disperse piecemeal; waste little by little (usually followed by away): to fritter away one's money; to fritter away an afternoon. 2. to break or tear into small pieces or shreds. verb (used without object) 3. to dwindle, shrink, degenerate, etc. (often followed by away): to watch one's fortune fritter away.

The lazy student frittered away his time, his parents' money, and his prospects for a prosperous future.

Maybe a little more vulgar than you're looking for, but a common British idiom for this is 'pissed away'.

"I pissed away four years of my life in university and didn't graduate." "The old mayor pissed millions of dollars away on stuff nobody wanted."

Examples from Wiktionary

The fable The Ant and the Grasshopper comes to mind.

One bright day in late autumn a family of Ants were bustling about in the warm sunshine, drying out the grain they had stored up during the summer, when a starving Grasshopper, his fiddle under his arm, came up and humbly begged for a bite to eat.

"What!" cried the Ants in surprise, "haven't you stored anything away for the winter? What in the world were you doing all last summer?"

"I didn't have time to store up any food," whined the Grasshopper; "I was so busy making music that before I knew it the summer was gone."

The Ants shrugged their shoulders in disgust.

"Making music, were you?" they cried. "Very well; now dance!" And they turned their backs on the Grasshopper and went on with their work.

From here.

You could borrow from this parable to say something like

His behaviour has been more grasshopper than ant.

and people who are familiar with the fable (it's a common fable) will know what you mean.