Is there an idiom for a wish or fantasy being fulfilled in such an excessive manner that it might be too much to handle?

"Biting more than one can chew", is used mostly for attempting to do something too difficult. What I'm looking for is more in the style of having a wish or fantasy, imagining how goold it would be if it became true, but then it gets fulfilled beyond expectations, and that has negative consequences, or at least it's too much to handle.

For a very rough example, someone wants to be richer, and then wins the jackpot on the lottery, becoming a multimillionaire. However, that new lifestyle leads to his undoing. Having won only a smaller sum, he could have improved his life with it, but winning too much ruined him.

Be careful what you wish for is a well-known adage. The phrasing of the latter half varies -- you might just get it, lest you receive it, it could come true. (The latter half is optional; you can just say be careful what you wish for.) The implication is that the fulfillment would be a curse, although not necessarily from overabundance. That thing you think you want, you might not actually want it.

If I wanted to mention that there are drawbacks to positive things, I might point out that the lottery winner's winnings were a double-edged sword, the metaphor being that the same thing wielded with power poses a major liability.

If I wanted to convey specifically the idea that the wisher might get too much of what they want, I might make an allusion to King Midas. Be careful, though: if you say someone has the Midas touch it will be interpreted forgetting the moral of the story, merely as indicating that the person creates great value in whatever they do.

In Greek mythology, there was a guy named Icarus who had always dreamed of flying. Someone made him a set of wings that enabled him to fly. However, they were made of wax and he was warned to not fly too high or else they would melt from being too close to the sun.

The wings exceeded his expectations. The higher he flew, the more wonderfully intoxicating the experience. And, eventually he flew too high, the wings melted, and he came crashing back to the ground. The end result being that in the long run, he would have been in much better shape had he flown at a "low and steady as she goes pace (snail wins in the end. he could've enjoyed an entire life of flying)" and not tried to live life like a rocket (ascending too high / too fast in life fills you with hubris, early success is like a drug, but then you crash, burn, and yet gain wisdom).

An idiom / metaphor based on this that I'm familiar with that sounds natural is "He flew too high, too soon, in his career." Applying it to other contexts could also work, but I can't think of any.