Having a plate full of salad . . .
. . . and realizing you don't have to eat the spinach. You can just lick the dressing off each leaf.
Having a plate full of cupcakes all to yourself. Forget the salad!
Singing all the verses of "Joyful, Joyful We Adore Thee" (opera version, of course) into a vacuum cleaner hose so that your voice is projected through the entire house bringing happiness to all.
Some people even think happiness is: being "successful" in a career, having a lot of friends, or . . . chocolate. But, I like the apostle Paul's definition--
Not that I am speaking of being in need, for I have learned in whatever situation I am to be content. I know how to be brought low, and I know how to abound. In any and every circumstance, I have learned the secret of facing plenty and hunger, abundance and need. I can do all things through Him who strengthens me. Philippians 4:11-13
True happiness then is being content, by God's strength, in any and every situation.
So, even if your salad doesn't have dressing (or worse, it's blue cheese), or if your mom finds out you have that plate of cupcakes (and takes it away), you can still be happy.