Actually no you are incorrect. There are requirements by law in the use lethal force in self defense. Generally put in the simplest way it goes by the "average man" rule. I.E. would an "average man" be threatened enough in a given situation to be authorized to use lethal force. If someone comes up to you and threatens you with their fists and you pull out a gun and shot them you would in fact go to jail. Why? It's considered a disproportionate use of force. Don't believe me? Look it up, or better yet talk to cops or a lawyer about it. Just because you have a gun doesn't mean you can use it no matter if you feel threatened or not. In any situation where you use lethal force you need to prove that your life was in fact in danger, "Self defense" won't cover it. Keep in mind that in murder cases where the murder admits to the killing over 90% of the time they claim it in self-defense. So when you walk into that courtroom the case will also not just be as clear cut as, "Hey he was a crackhead trying to rob me, he showed a knife in his belt so I shot him!". There is more to a case than just that.
Also in the American court system, life is normally given priority over property. Not in all states, and it varies country to county, but for the most part that statement holds true. If someone jacks your shit and you shoot them as they run, you more than likely depending on your state/county will in fact be going to jail for at least manslaughter.
Read up on your rights as a gun owner to self defense. When you use a gun for protection, especially outside of the home, you are fighting an uphill battle.