Some problems should not be solved, because they cannot be solved, and therefore must not be solved. Such problems are instead to be let go of.
Examples include:
Changing other people when they have proven themselves unwilling to change again and again. Stop trying to change them and accept them as they are, or else let go of them entirely or, less extreme, distance yourself as appropriate.
Making improvements in products and services that are not strictly necessary. These small improvements come at the cost of more important features or even whole new products. Stop pursuing diminishing returns; it’s an infinite amount of work for a finite and modest benefit. (See also: 80/20 rule.)
Thinking and worrying about things outside my control or knowledge. Either bring it within my control or knowledge, or let go of it entirely.
Letting go of insoluble problems is not laziness; it’s wisdom.