I've been practicing this technique for quite some time and I must say that it's usage has payed off in a great way.  Whenever I begin to feel down for whatever reason I can call upon one of my several programmed physical cues to incite an emotional/chemical response that lifts my spirits.

A physical cue is simply a particular touch, movement, or automatic behavior that you associate with certain feelings in order to create a systematic response to the re-occurrence of the movement.

In other words...It's a life hack that promotes a general feeling of happiness, just like a smile, which can cause a mental shift in attitude.

Choose a particular movement or touch that you perform regularly, and begin programming it with memories and thoughts that bring pleasure.  If you encounter an experience that brings you joy, use that motion you've chosen to continue programming.  After several weeks of programming if you feel you need a pick-me-up at any time try using your cue and watch as those emotions come flying at you.

At first I would swipe my hand across my forehead whenever I recalled an emotional event that brought me joy, or a new exhilarating experience occurred giving me more ammunition for my programming.  After several weeks of incorporating this habitual movement into my routine I decided to test the effects out.  Each time I would swipe my forehead flashes of those memories and their connected emotions would rush back.

If you've ever been a smoker you can understand how this works.  We program ourselves with the actual use of nicotine, and then associate the hand-to-mouth movements, the feeling of fullness in the mouth etc., with the pleasurable feeling.  This is why it is recommended upon quitting to replace these movements with similar objects, only without the harmful tobacco smoke.  (Think chewing gum as an example)  The reason these physical cues work is because the body, being trained to the physical motion of smoking, has programmed itself to begin a reaction, in which dopamine (key to pleasurable feelings in smoking and other addicting activities) is released, upon fulfilling that desire.

Give it a try (you've got nothing to lose.)