You've got to forget the past and start living in the present.

你必须忘掉过去，开始现在的生活。

Let's forget the past.

让我们忘掉过去吧！

We don't forget the past days.

我们不要忘记过去的日子。

I want to forget the past thing.

我想忘掉以前的事。

Forget the past. Forget yesterday.

忘掉过去，忘记昨天。