This is a good saying and sometimes true, but mental illness is usually a forever problem. I don’t say that to disparage it either; depression, anxiety, schizophrenia, and internalized abuse fucking suck and it takes a while to tear down the self preservation instinct to the point where an ending can seem appealing, even if just for a moment.
This is why we need to legalize psychedelics. When paired with counseling, they can create moments where you can see alternatives, which gives therapy a solid shot at success even for advanced cases.