Capacity expands when responsibility is introduced gradually and repeatedly.

Capacity does not grow from a single large demand, which tends to break rather than build. It grows from being given slightly more than is comfortable, repeatedly, with enough recovery in between to absorb it. That is how strength works physically and it is how it works with responsibility, difficulty, and pressure as well.

If you want to handle more, take on something a little beyond your current comfort rather than a great deal beyond it. Let it become normal, then do it again. The gradual version reaches much further than the dramatic one and does not cost you a collapse.