It is a common phrase used to express that something is happening or will happen without the speaker's involvement or presence.
Here are some examples:
* "No puedes hacer eso sin mi." (You can't do that without me.)
* "La fiesta fue aburrida sin mi." (The party was boring without me.)
* "No se puede vivir sin mi." (You can't live without me.)
It's important to note that the meaning of "sin mi" can vary depending on the context. It can also be used in a more figurative way, like when someone is saying they will not allow something to happen.