You can lead a horse to water

You can lead a horse to water (but you can't make him/it drink).

something that you say which means you can give someone the opportunity to do something, but you cannot force them to do it if they do not want to. I made all the arrangements, bought the ticket, and even took him to the airport, but he just wouldn't get on the plane. Well, you can lead a horse to water, but you cannot make him drink.

See also: can, horse, lead, water