You will be given a certain amount of leeway if you can establish that you were not the initial aggressor, meaning you did not start the fight or was the first to draw a weapon. However, you can still face criminal charges if you continued to exhibit aggression or use force after the threat is over or neutralized. This ironically turns you into the initial aggressor. This could be true even if you acted to protect yourself or others.
Arguing self defense is the best defense when you are facing allegations that you either exhibited force or used force against another. The law does not require that you render yourself helpless and subject to whatever threat comes your way. However, if you choose to use force to defend yourself or defend others, you need to be sure that you act within certain boundaries.
If you can successfully show that you reasonably believed that you or another person was in danger of suffering imminent harm and that you did not use more force than was necessary to defend against that harm, you would not be convicted of brandishing a weapon pursuant to Penal Code Section 417. Therefore, arguing self-defense or the defense of others within these constraints can protect you against a conviction. Any deviation from these constraints can result in an imperfect self-defense argument that can only act as a partial defense that still exposes you to some criminal penalties.