Take clues from your colleagues known for being positive and happy. Have you paid attention to how they speak? Most of them, you'll note, refrain from negative words, speech, or conversational topics because they know the stressful effects it has on their emotional well-being. They stay away from unnecessary drama, malicious gossip, and psychological warfare.
Helpful tip: When you're present and "in the positive," offer other people helpful feedback that empowers and lifts up. Doing so will inspire greatness in others, build trust, and generate happiness in your own life.