When you wake up, say to yourself “something good is going to happen today.”
Then walk through your day knowing “something good” will happen. When someone calls think to yourself “is this the good thing?” and answer the phone like you think it might be. A friend walks up to you, are they going to tell you good news? Look at them like that.
Anticipation, expecting something good is part of this overall sensation of feeling happiness. Replace “what tree is going to fall on me next” with “what excellent news is going to show up for me today?”