In order for you to have a justifiable “self defense” claim, one of the five elements required is “imminence.“
This means the threat is immediate, so pressing you have no time to call for help. The threat is timed so a reasonable man or woman would employ an instant defense. Any hesitation could result in grave bodily harm or death. The timing of your response is critical to you case. You cannot use defensive force too early. For example, if I were to say “I am going home to get my gun and shoot you,” the threat is not imminent. One appropriate response would be to evade the threat, go to a safe location call the police. Your attacker must have the ability to harm you, he must be close enough to access you, and his words and actions must indicate he is about to follow through with the threat right now. Being close enough to access you may depend on his weapon. For example if his weapon is a gun, he can access you quicker from a larger distance than he could with a club. One good tactic is to always try to maintain distance between you and the threat.
You can also respond too late to an imminent threat. For example, your attacker knocks you down, takes your wallet and runs away. If you pursue the attacker and bludgeon him with a club, this will be seen as retaliation not self defense. Since the threat has already passed, your actions will be considered a separate crime from the original attack. Innocence was the first, Imminence is the second element in your self defense case. Success will be in your favor if your mind and body are well trained. Know your rights and the law. There will be more to follow on the third element of a self defense case.