You never know till you try
You never know (what you can do) till you try.
Prov. Even if you think you are not able to do something, you should try to do it. Jill: Want to go rock-climbing with me this weekend? Jane: Oh, I can't rock-climb. Jill: How do you know? Have you ever tried it? Jane: No, not really. Jill: You don't know what you can do till you try. Alan: I'll never be able to learn to dance. Jane: You don't know till you try.