Self-defense is what happens when you are losing, Rory Miller (Meditations on Violence) says:
What does that mean? That the bad guy picked the range and his position. That he probably moved in such a way as to hamper your response (amazing how real knives are almost always used after grabbing the head or your arm and unbalancing and how few people practice against that). That before you are even aware things have started, your structure is compromised and you have taken damage.
Whatever your best move is, how well will it work if you are already folded over with your wind knocked out, wedged into a corner and with the bad guy riding your closest arm and slamming strikes into the back of your head and neck? ‘Cause that’s the baseline, my friends.
And you can fight from there… but you have to practice fighting from there. There are ways to use a compromised structure or the momentum of being slammed.
Bad guys have it easy. Almost any technique from any system will work if you are the bad guy. You can pick the range, the target and the orientation. From target shooting to soft arts, almost anything works if you can choose the when and where. Only the bad guy ever gets to choose that.