In some new age circles, it is fashionable to say that we never get more than we can handle.
This is obviously bogus in a conventional sense. Lots of people have breakdowns, go insane or commit suicide because life is unbearable to them.
At the same time, these are ways of handling an unbearable situation, so they are handling it in that sense. Breakdowns, insanity and suicide are safety valves for unbearable situations. (The new age folks probably don’t mean it in this way.)
Yet, there is some truth to the statement as well. If we are trained, for instance in meditation practice, we develop a capacity to be with and allow whatever is happening. We may even find the opportunities and gifts in it, turning it around to something valuable to ourselves and maybe others.
If we are able to do this, either through the luck of genetics or upbringing, or a disciplined practice, then the advice is for ourselves. We can ask ourselves, is this more than I can handle? And the answer is usually no.
But others may not be in the same situation. They may not have the tools to work with and relate to whatever happens in this way. The statement then becomes heartless if used towards folks in this situation, or as a general rule.
Finally, the statement is definitely true for what we are. As awakeness, we are untouched by whatever experiences are there, no matter how intense and apparently unbearable. Just as space is not touched by whatever happens within space, awakeness is untouched by its own content.