Gun for self-defense - prerequisities

You might prefer other self-defense options, but my favourite is a gun. Do you know a saying "God created men and Samuel Colt made them equal"? Even if an attacker is physically much stronger than you, a succesful counter-attack is always possible with a gun. However there are some pre-requisities:

1. Concealed carrying - an attacker must not know about the gun in advance, because he could prepare for it (quick attack, his own weapon)... moreover it is mandatory by law in many countries anyway
2. Proper training - a gun is useless if you are not able to withdraw and load it under all conditions and stress
3. Mental preparation - it is better not to have any gun than to have one and not be able to shoot (because then a thief will take it away from you and use it against you)

If you have no issues with the points above, the next step is to choose a proper manufacturer/model. I will write about it next time.