How can we ever know for certain if we live in a simulation, if we can not look outside the simulation in which we live? Assuming the cause that created the simulation lies outside the simulation, and that we can never escape the simulation.
The same question in other words: How can we ever know for certain if there is a God who created the universe, if we can not look outside the universe in which we live?
Maybe the best advice is to go out there and live really interesting lives and do unexpected things so that the computer simulation won't get bored and shut you down.