To unlock the I get knocked down... trophy in WWE 2K19, you need to use the Payback Instant Recovery ability against an A.I. opponent in Play mode.
Jeff Hardy has this trait, so make sure that the ability is selected as the yellow option in the setup before the match starts. Now in the match you need to take a bit of punishment until the yellow circle beneath your wrestler's name is filled up. You will get an opportunity to use the Instant Recovery ability as soon as that yellow circle is full and there is an opportunity to instantly recover from a knock down. The circle will flash when you have the opportunity to do so -- press L1 and R1 to use it.
Once you use the ability the trophy will unlock shortly after.
Here's a short video demonstration from Dan the Delight: