Res ipsa loquitur — The facts speak for themselves.
This is good advice, especially when writing about oneself. Show the reader through examples and anecdotes. Do not tell the reader by making unsubstantiated assertions.
“I am a hard worker who always perseveres to the very end.”
Everyone sees themselves as hard workers who persevere. Have you ever known anyone to describe themselves as a lazy quitter? Probably not, at least not in writing, even if they are lazy quitters. Especially if they are lazy quitters.
Rather than a slurry of empty assertions, simply state facts. For example, a college student who worked 30 hours per week to earn money for tuition, volunteered 5 hours per week at a hospital, and graduated with a 3.9 GPA is obviously neither lazy nor a quitter.
Res ipsa loquitur. Enough said.