Except if you happen to live in a country where guns are illegal, where the chances of your life being ruined by being unarmed is far lower than the chance of your life being ruined by being caught with owning or using a gun.
In Q1 london this year there where 290,000 stop and searches leading to 10,000 arrests, which in an urban population of 8,000,000 is about 3% chance of getting searched, if you're a young male that percentage goes alot higher, much higher than the chance of actually having a use for a gun.
The penalty for possession of a firearm in the UK is minimum 5 years, and if you use a gun, even in self defense, you're likely to get 10+, meaning the only time it would ever be wise to use a gun is if you were planning to use it and dispose of it immediately afterwards, otherwise a tire iron or a baseball bat are both semi-legal depending on where you're carrying them
Also, how many people here saying its important to do X, Y and Z in a gunfight have actually been in a gunfight?
21. Be polite. Be professional. But, have a plan to kill everyone you meet if necessary, because they may want to kill you.