It is easy to think you are ready for an attacker because you have a weapon. When one comes at you, you might whip out your defense spray and promptly miss. This could get really ugly if your assailant has a knife.
Use the 2 oz. Fogger Practice Pepper Spray for practice before you try using the real thing on a live target. It contains only nitrogen-pressurized water so you do not waste actual pepper spray while learning.
The non-lethal burning pain that pepper spray induces will last for quite some time, but attackers will not suffer lifelong damage.
WARNING: Do not spray on anyone or yourself. Even though there is nothing in the sprays to do any permanent harm to anyone, the nitrogen can cause some skin irritation or burning if sprayed in the eyes.