Using a firearm defensively is not an "opportunity". I don't mean to be condescending but I think it's an important clarification. Even drawing a concealed weapon can be construed as use of deadly force and is only justified in certain situations for example if the carrier is attacked using deadly force they can respond with deadly force. Deadly force can include more than one attacker (a guy versus two attackers) or a huge difference in strength or ability (an average woman versus a male attacker) or of course an attacker with a weapon such as a gun, a bat, or a knife. I've even read that certain unarmed action such as a choke hold can be considered deadly force. When I carry a defensive firearm I'm not walking around looking for "opportunities" to use it. I absolutely avoid any situation where I even think there's a possibility I'd have to use it. It's a last resort. I'm the nicest, most polite, passive person you've ever met especially when I'm carrying. I absolutely do not want to draw that weapon! You're thinking "then why carry one?" Well I've learned that I don't get to decide when I might need it so I want to have it available to defend myself and my wife. There have been a few times when I was very glad I had it. One was camping on a designated campground where me and my wife (girlfriend and the time) were the only ones camping. Around dusk a sketchy looking Suburban with two scruffy occupants started slowly driving back and forth past our campsite looking at my wife and I, mostly at her. I'm not a paranoid guy but we were both pretty sketched out. We couldn't leave because we had both had a few beers with dinner and didn't feel comfortable driving and the Suburban was on the only road in or out. At one point when the Suburban was out of sight turning around I went into the tent and put my holstered pistol on my belt (this was an open-carry legal state and guns were allowed at that campground). I don't know if the guys saw the gun or not but they drove past one more time and left. I'm glad I didn't have to draw it but I sure was glad to have it. I also want to point out that in no way did I touch, motion to, or in any way try to use the gun as a threat. That would be considered brandishing.
Another situation was when I lived in the second story of a three story apartment building. A guy moved into the fist floor apartment who I'm pretty sure was some kind of drug dealer. He had a pretty nasty pit bull (nothing against that breed but this one happened to be pretty aggressive). One day I get out of my car and go to walk up to my apartment and there was the pit, unattended, guarding the stairs with its fur up. I started backing away but that seemed to provoke it. I was sure I was about to be mauled and started drawing my pistol in case the dog lunged when the neighbor came out and called the dog in. He saw the gun in my hand and kind of looked at me funny but didn't say anything. In retrospect I probably should have reported it to the police but I didn't know any better at the time. We moved out of there pretty soon after that incident.
I guess the overall gist is that I carry because I want to be able to protect myself and my wife and I know that violence can happen at any time. I carry unless I'm going someplace where it's prohibited like to my job. I consider drawing a gun an absolute last resort and a failure on my part to avoid trouble. Hope this answers your questions, feel free to reply or PM me if you have any more or would like clarification on how concealed carry works!