Translation of "Optimist" in Chinese

You're an optimist.

你是个乐观主义者。

- I am an optimist by nature.
- I'm an optimist by nature.

- 我天生是一個樂觀主義者。
- 我生性樂觀。

- You're optimistic.
- You're an optimist.

你是个乐观主义者。

Helen is by nature an optimist.

海伦是个天生的乐天派。

I am by turns an optimist and a pessimist.

我时而乐观，时而悲观。