One day I came across the words 'inner smile' and I couldn't get them out of my head for days. I think it was advertising a seminar. Why was this so important? And then it struck me! The main characteristic shared by all the people I admire in the world of tai chi and beyond was their inner smile.
What is this inner smile? Well, you notice it in the eyes most of all. It says 'I love life'. It's a reflection of pure radiant healing light, a place of love and joy.

So how to cultivate this inner smile?
I think the most important thing is to allow it to happen. The emotions are the driving force - the horses - harness the horses and many things become possible. But where is the driver? We are pulled this way and that to the extent that one wonders if the driver actually exists. So many people these days seem to be driven by fear, envy, greed, ambition (those horses again but this time in a negative context) or simply bowed down under the weight of responsibility,or too busy to let this healing light into their lives. Adapting and updating this image (horses -> horsepower) Mantak Chia likens waiting for external conditions to give us joy to 'sitting in a car waiting for someone to give it a push' instead of starting the engine!

Yes but how?
It is all closely linked with relaxation techniques and meditation. In another image from Mantak Chia, think of the mind as being like a puppy that needs training. You must train the mind to behave itself and think more positively and compassionately otherwise it will just make a lot of messes! Maybe you are good at visualisation. If so you might like to focus on the image of someone smiling at you benevolently. If on the other hand, like me, you are more oriented towards the sense of touch, you might like to imagine being held in a trusting loving supportive way, or perhaps enveloped in a cloud of love.
Use this image or feeling to help you relax your mind and body and surrender your cares to the universe, God etc. Let the feeling spread throughout your body, sending love to all parts of your body. Not just that, but extend the loving feeling beyond yourself to other people, animals and beyond and given time who knows what might happen.