賣仔莫摸頭 (maai6 zai2 mok6 mo2 tau4) — one should be resolute (harden their hearts) and be willing to let go once they have decided on something (especially when compelled by circumstances) and not allow themselves any chance to renege in Cantonese
maaiˍ₆賣zaiˊ²仔mokˍ₆莫moˊ²摸tauˎ₄頭简 卖仔莫摸头
Mandarin Pinyin: mai4 zi3 mo4 mo1 tou2
Meaning of 賣仔莫摸頭
nounone should be resolute (harden their hearts) and be willing to let go once they have decided on something (especially when compelled by circumstances) and not allow themselves any chance to renege