The Tui Shou, or "pushing hands", can be relaxed and fun if you do not oppose yourself with force and fight like a bull.
Fighting like a bull is not the philosophy of Taijiquan.
From the forms and models of study it evolves into "formless".
In the advanced level the Tui Shou eliminates the different push patterns with his hands and intercepts an attack with reflex actions, without thinking.
To reach the level of reflex actions, years of daily training are needed in the practice of Tui Shou.
Life is short, but art is long. It takes a lot of practice if you want to effectively use Tai Chi Chuan for self-defense.
The forms of Tai Chi Chuan can be practiced in pairs giving rise to a dynamic sequence, San Shou, preparatory to free fighting.