sell someone/yourself/something short

US /sel ˈsʌm.wʌn/jʊərˈself/ˈsʌm.θɪŋ ʃɔrt/
UK /sel ˈsʌm.wʌn/jʊərˈself/ˈsʌm.θɪŋ ʃɔrt/
"sell someone/yourself/something short" picture
1.

niedoceniać, umniejszać

to underestimate or undervalue someone or something

:
Don't sell yourself short; you have a lot of valuable skills.
Nie niedoceniaj się; masz wiele cennych umiejętności.
It would be a mistake to sell them short in this competition.
Byłoby błędem niedoceniać ich w tych zawodach.