I agree with you Jose. If someone is so unsure of their own ability to safely handle a firearm, then they probably shouldn't be handling one.
However... if someone simply has the "beginner nerves" ie: isn't totally comfortable handling a firearm YET, let alone carrying one on a daily basis, then it's just a matter of time before they get comfortable.
MXD, most, if not all of us who carry everyday chambered... had the beginner nerves on our first days/weeks. I carry chambered because I'm of the opinion that an unloaded gun (unchambered) is useless. And I believe that thinking you will have the time or the ability to have two hands free to draw and rack the gun while in a fight for your life is doing yourself a disservice. (there are many reasons why you would only have one hand free, etc)
When I first started carrying the first step I had to overcome was understanding that the gun, while chambered, was NOT going to do anything unless I made it do something. And by "made it do something" I mean pulling the trigger. If I do not pull the trigger the gun will not do anything. Rule #2 of safe gun handling. And no matter how much you drop/knock around/kick your modern-day firearm, it WILL NOT GO OFF unless you pull the trigger.
Once I ingrained this "trigger off the finger" rule into my head (along with the other 2 safety rules), the next thing I had to do was become comfortable with handling and carrying by consciously following the safety rules 24/7.
And I say "become" because most of us don't start out completely comfortable. It's something we must do deliberately and carefully, something we must practice. And with practice comes the confidence in yourself to be safe with the gun.
Go as slowly as you need to while handling/transporting/drawing/holstering, etc while consciously making sure you're following the safety rules. If you go too fast, it's very easy to make a mistake. Ask me how I know. (No ND, but could have been. And you can bet I'll never make that mistake again!)
If you discipline yourself to always handle your firearm deliberately, always consciously following the safety rules while that gun is in your hand, you will be just fine.
Chamber your gun. Go slow. Take your time. Understand the fundamentals behind each rule of safe gun handling (why each rule is there). If you understand why the rules are there, and you make it priority #1 to follow these rules, you become more comfortable and confident in your ability to be safe.
Then again, I've been known to be wrong.