Most of us reacted to the news with cautious/guarded 'optimism'. [=a feeling that something good may happen but will not definitely happen]
He maintains a sense of 'optimism', despite all that has happened.
The early sales reports are cause/reason/grounds for 'optimism'.
(..) begun rounding up suspects. His Majesty has been informed of the theft. He is flying home... from Washington. I expect an arrest any moment now. I do not share your optimism. We know the culprit is still within our borders. All the airports... and railways stations are being watched. (..)1975 The Return of the Pink Panther