Tell each other about that smile the customer had on his face when trying out your new product. Or about that new line of code you just made. Or that new tool you tried out. Or that new theory on working smarter.
Saying out loud, enforces the successes you make as a team.
Share them at retrospectives, but also daily where the whole team is present, at daily scrum e.g.
Additionally sharing means bonding, and also adds to your teams collective knowledge and capacity.
Also remember to tell about failures and episodes that made you smarter – it enforces a culture where you make room for failure and learning together, and ultimately takes your team further.