Дай глупому лошадь, он на ней и к черту уедет

Some men given enough freedom of action will eventually overreach themselves, cause their own downfall, or cause trouble. See Заставь дурака Богу молиться, он и лоб расшибет (3)

Cf: Action without thought is like shooting without aim (Am.). Beggars mounted run their horse to death (Br.). Give a beggar a horse and he'll ride it to death (Am.). Give a calf rope enough and it will hang itself (Am.). Give a fool (a thief, him) enough rope /and he'll hang himself/ (Am., Br.). Give a man rope enough and he'll hang himself (Am., Br.). Set a beggar (a rogue) on horseback, and he'll ride to the devil (Br.)