In Doctor Strange, the Ancient One knows that she is going to die soon because she cannot look past a point in the future, and believes it to be when she will die.

However, we also know from Infinity War, that Doctor Strange was able to look past the point of his own death, and determine how to undo the “snap”, but we can put that down to the assistance of the eye of Agamatto and the Time Stone.

However, the question remains: Why is it that you can’t look into the future past your own death?