You can lead a horse to water, but you can’t make it drink.
~ English Proverb
The above is the oldest English proverb in existence. While there are older sayings around, they derive either from Greek thought or from the Bible. The above idiom is purely English, although it’s original form was a bit rougher in spelling and words.
Simply put, you can offer water to a thirsty horse, but if it stubbornly refuses to drink, then there isn’t that much you can do about it. Likewise, you can offer advice or assistance to a person who desperately needs it, but there isn’t much you can do to force a course of action upon them. Obviously, I’m talking in generalities here, and there are times when someone might have to be forcibly restrained (legally, obviously) to prevent harm. Even then, a person can react in such a way as to make a matter better or worse.
I have seen it in my own life, and I have seen it in others. Unless something comes and shakes things up to get our attention, we can deceive ourselves in so many ways. I have finally come to the conclusion that we are our own worst enemies.
While pondering the spiritual implications of this, there are so many applications that it boggles the mind. However, I think there only is one that can sufficiently sum it up:
9And the great dragon was cast out, that old serpent, called the Devil, and Satan, which deceiveth the whole world: he was cast out into the earth, and his angels were cast out with him. (Revelation 12:9, King James Version)
You can stick the horse's head in the water until he drowns.
You can also lead someone to a conclusion but you can't make them think.