The following dialog is for questions 3 to 5.

Indira: You know what? I have to run for 5 km in less than an hour next week in the school running competition. I don't think I can do it.

Arif: Let me ask you. Have you tried to do it?

Indira: No, I haven't. I can't run fast, you know.

Arif: Please listen to me. You should not lose your self-confidence.

Indira: I don't lose it, but I know my limit.

Arif: Don't say that. Convince yourself that you can do it. You just need more practice.

Indira: I know it, but ...

Arif: No more argument. Let's jog tomorrow morning to strengthen your muscles. Everything's possible!

Indira: All right. Thanks for always supporting me.

Arif said, "Convince yourself that you can do it."

What is the synonym of the underlined word?