“…….I have heard from countless lecturers that Hashem doles out nisyonos and tribulations that an individual can tolerate. Hashem does not dish out more than a person can handle…..”
We’ve all heard that too, but where is the mekor for that?
The best I’ve heard, is that this is based on a Chazal that says that Hashem doesn’t hit with 2 sticks at once.
Whatever that means, we, however , see people who’ve been broken by traumas in life , practically forever.
Broken hearts, nervous breakdowns, suicides, mental derangement, etc.
Your question is stronger than the answers we’ve been given..