This shirt is a fun play on words, stating "yinning at life". This phrase, of course, refers to the famous image of the yin and yang, which is displayed in the middle of the shirt.
The yin and yang has famously represented the idea of two opposite or contrasting forces coming together and complementing each other really well. In a larger sense, it is supposed to mean that things that may not seem like they are meant to fit together can actually be intertwined and related in unexpected ways. Wear this shirt to show everyone that not only are you winning at life, but you are also "yinning". Use it is a reminder to find common ground with people you wouldn't think you could.