There is no reason to be pessimistic about the future, because we are young enough to do everything.

没有理由对未来悲观，因为我们还年轻，我们能做任何事情。

Don't be pessimistic about my plans.

不要对我的计划那么悲观。

There is no reason to be pessimistic about the future.

没有任何理由对未来持悲观态度。

They may believe that a negative situation will never change and be pessimistic about their future.

他们可能认为消极的情况将不会改变并且对未来感到悲观。

The nation with the thickest and most expansive networks will define the age. There's no reason to be pessimistic about that.

美国用最密集最广泛的网络定义了那个时代，没有理由悲观。