Being positive is widely assumed to be a better way to be. It is often seen as a contrast to being negative or overly critic.
And yes, criticism is often the opposite of being productive.
The reference for being positive and being negative is reality.
Reality is the space in which we do the work and results happen.
Where there is activity, there is also the opportunity to learn.
Learning happens by being open and being able to see the things we can make better.
Accountability is the posture that invites to see errors as opportunities to learn.
Acknowledging failures and success as simply existing helps to use them to learn.
It also leaves room to deal with the frustrations of failure and the satisfaction of success.