In the question posed here: No Limits Humans, I asked if having the ability to instantly replace tissue in the body (and being aware on all levels that you can do so, kinda like a Matrix "believe") would increase your speed and strength. The answer was yes, but not by much. But now we take it from how much the body would benefit and look at the mind. If there were people who were 100% healthy. Would they be smarter, have better reaction times? Would there be any other noticeable side-effects to have a brain that can heal itself as fast as you injure it?
This is a very interesting question. Does the body repair only affect the body? And where is the limit of fixing the body vs. fixing the mind? Many mental issues are caused by chemical imbalances, including ones that are self inflicted.
So would downing a quart of vodka like a beer bong, be purged as poison, or just metabolized quickly or would the body just repair damage done to the brain while marinating in alcohol?
Some depression is a normal phase for people to go through, others get in a feedback loop and need help getting out. Would the healing keep the brain a nice healthy level of different chemicals? Not letting someone feel depressed? Or kick in when things are too severe or taking too long to recover?
These make a difference because, if strong emotions are 'damaging' then these people will tend to be very solid and unflappable. Not much will upset them at least not for long.
If on the other hand only physical 'health' is taken care of, then we are going to have much more interesting range of people. Some will become dare devils pushing to see how far they can go can I jump this 30ft. between rooftops? Can I piss off that cop enough to get him to shoot me? etc. This could also lead to depression, for any number of reasons. Survivors guilt, they always live while so many die by the hands of the monsters they hunt, and there are always more, could be one. They could become very aloof or sociopathic. After living through a hundred deaths and killing untold monsters for a century you'll likely get a little jaded. On top of that any friends or family not 'one of you' will age and die away. It will start to disconnect you from humanity. They might start seeing themselves as 'gods'.
Some people might break under different severe injuries happening over and over, but still waking up with the memories of those injuries. Say losing limbs or having your chest crushed. They might just try to find some way to make it a permanent end.
Some might become more aggressive, willing to push their views on others because they can and after seeing so much believe themselves to be unerringly right.
And of course some will just withdraw from humanity, not interacting with them, unless they have to, such as saving the world again.
I suspect that without "limits" the person would eventually become sociopathic, becoming unable to interact normally with the other, unenhanced people around them.
IF you were capable of rapid regeneration and able to push your body to the very limits of human ability, your views of mundane human beings would begin to change. You might feel pity for them being unable to do the things you do, or resentment for them asking you to use your superior abilities on their behalf, of even a sense of smugness because you can do things that no one else can. Now imagine having these feelings 24/7 for every single person you meet.
Since these powers are not exactly supernatural, the enhanced person would essentially be "Batman", who is depicted as the epitome of human development, being vastly smarter, stronger and gifted with a wide range of superior skills compared to everyone else (You might be a black belt in a martial art, but Batman knows virtually every martial art ever created, as well as how to bend science and technology to his will: take that, ordinary man!). Batman, of course is not exactly the sort of person you would be spending a pleasant afternoon with (unless you have some very strange ideas of what a pleasant afternoon consists of); for the most part, you would be a piece in his larger game. Another fictional example might be Sherlock Holmes, who is also an example of a superior being, and who largely no longer interacts with people, except for a very small cadre of trusted friends like Dr Watson and Mrs Hudson, and cultivating a crew of agents in the form of the Baker St irregulars (who may not actually know who Holmes really is).
While enhanced people might not be violent sociopaths, they most certainly won't be sharing many interests in common, and certainly can't share a large part of their lives with you and I.
If you believe that the brain is the source of the mind then it will clearly make a huge difference.
Almost any disease can affect the brain. A virus can wipe out your short-term memory for example. This means you can only have memories from before you were affected. Anything new is forgotten in less than 30 seconds.
Phobic fears and post-traumatic stress reside largely in the amygdala. By selectively replacing it you could remove old fears.
There are many reason why the ability to repair and modify the brain would be useful - curing certain types of blindness for example.