Here is an explanation using the idea of a deck of cards. A complete deck consists of 52 different cards. But within a very large number of games, their combinations will inevitably start to repeat because the number of different combinations are limited. The same principle works in the Multiverse because according to the laws of nature, the primary constituents of matter — or particles — are like a deck of cards: at each point in space, they can be arranged in a limited number of ways.
If space is infinite and if the number of universes is also infinite, then such variants must be repeated. And since each of us is just an option of particles assembling, somewhere there must be our exact copies.
On one hand, this is depressing because it means that we are deprived of uniqueness- you are a copy or version of one of the lives of some other combination of particles.
On the other hand, if this is not a utopia and the universe is really infinite, then somewhere in the depths of distant galaxies, you are doing what you wanted. You have achieved completely different heights. Maybe you once made an important decision that helped you to exist at all.