У робкой кошки мышь резвится

you are bashful or servile, others will dominate you. See Кроткая овца всегда волку по зубам (K)

Cf: A blate cat, a proud mouse (Br.). Не that makes himself a sheep, shall be eaten by the wolves (Am.). Make yourself all honey and the flies will devour you (Br.). Make yourself honey and flies will devour you (Am.). A shy cat makes a proud mouse (Br.)