I'd say most of single-sentence advice falls under "dubious" advice, as it really lacks any kind of nuance. It can be a guideline and perhaps words to live by, but it will rarely help in concrete situations where more specific context should be considered.
My mum always used to say "Everything works out in the end" or something else equally trite until the day I snapped "Yeah thats why theres a suicide help line, because everything always works out in the end for everybody."