Having a conversation with someone who you didn't know was going to offer you a job when you need one. Sometimes the job you like can just happen by chance.
When you find that one song that perfectly fits your mood and then every song on shuffle somehow just gets you just right until the end. Occasionally Spotify gets me. Other times I have to go back to Pandora for a nostalgic time.
When you have a plant take over your grow space against all odds.
I have many more little things that make me happy.