When you play push hands you need to relax.
The reason is when you relax you can harmonize better. This allows you to join, harmonize and lead which is a lot like dancing where one partner leads and the other follows as can be seen below :-
Stanley is not my Tai Chi student. He is learning Sam Kuen Do (三拳道) via my FB SKD group.
I did this demo to explain some point about borrowing energy. I asked him to give a little resistance and he gave a tiny bit but its enough for me to use it.
I didn’t tell him what to do or not to do. I let him react however he wants to react. And it does look like an out of synch dance.