As far as being able to fight, yes I can fight if need be and have successfully defended my self unarmed before, however, It is not recommended as there is always a better fighter about, unless maybe you are Chuck Norris. In my case one hit to my pacemaker and I'm collapsed in pain. Yes, I was 38 when I had to have a pacemaker installed.
My understanding is that unless there is an obvious disparity in force, I'm NOT legally justified in drawing a deadly weapon to defend myself against some guy who just wants to kick my butt. I also realize that: 1) days of the old fashioned fist fight are either over or never existed, 2) There is always a tougher man than me just around the corner. Life is complicated and the situations we find ourselves in are often not simple. All that said, I'd rather recover from and old fashioned butt kicking than a murder charge due to undue use of deadly force.