I don't get what you mean when you talk about "productivity". Can you elaborate?

As for negative feelings, they're not always something you can snap out of and move on. There's something going on inside him, something that feels deep that is putting a crimp on him.
It is recommended that a Bipolar person gets some form of treatment, at least a therapist to work out on what is going inside him - his mind, heart, soul...
Wanting to be alone and having an attitude is probably the depression side of the mental illness.
A more general point, but bad feelings need a room at times. They can't always be solved with words or reminders to be positive. Accept a bit of it yet expect gradual treatment.
And make sure to make room for lots of love for your upcoming additional loved one