Ordinary lay persons are terrible at interpreting their own personal limits.
Similarly, most peoples are even worse at interpreting the internal states or limits of others.
As a rule, what is most productive is the commodification of consistent competence. Humans are however capable of vastly more than their comfortable pace suggests.
This “vastly more” however comes at a price. Psychological change is the most difficult thing for humans to undergo.
Try quitting caffeine or nicotine for instance. Or eat well and get regular exercise. These things will make anyone infinitely better off, yet are enormous undertakings.
Similarity, bringing forth the highest part of your capabilities are insurmountable without deliberate motivation, and TIME.
Pushing past, and redeveloping limits are certainly possible in most if not all, yet unlikely until the subject is ready to commit.
Some can see this in others, though it is a quandary which can destroy an otherwise good relationship if taxed.