When your back is backed up against the wall, that’s when you know no one can sneak up behind you you can focus on the frontal assault you can defend yourself with undivided attention.
So, when you can’t back up any further count yourself fortunate. Brace your back heel against the foot of the wall, raise both fists and smile.
[No, not ‘smile’.]
Set your mouth in a maniacal grin and giggle deliriously and in that next half second while your assailant pauses to shake their confusion in that half second you have your chance –
Punch them in the gut! Follow up with an upper cut and kick their ****.