On the subject of the OP question, maybe. Have had several years of martial arts training. Have had a few rounds of bar fighting and other assorted shenanigans. Read and watched assorted self-defense techniques (which I believe that if you ingrain it in your mind can help although may not be Bruce Lee pretty).
Now, if the question pertains to the bullshittery that is overtaking our world with the piss ant tactics used by so-called ISIS wannabes, then no, I don't think I could defend myself against them. Pop up out of nowhere, blow themselves up without any type of warning. Pull semi- or automatic weapons from their Netheryeya and unload on the crowd. Duck and cover time. Maybe find someone with a weapon and take it from them to use to defend yourself.