In my experience, having a stable girlfriend for the past 3 years has been like looking in a mirror every month or so.
She calls me out on things that I do habitually or without thinking, usually because they are selfish and hurt her or our relationship in some way. These are habits or personality traits that my close friends and family wouldn't be aware of, but that my girlfriend has exclusive access to as the one with whom I share the most intimate details of my life. She forces me to reflect on why I am the way that I am; sometimes directly when we fight, but often indirectly through her questions and observations.
I'd like to think that our relationship has made us more empathetic and introspective. I don't think it has made me any less extreme in my ideals though.
My personal view is that extremism is generally bred by a low standard of living and a high degree of economic inequality that is forced onto a united group of people that feel like they deserve more than the system has given them. The uniting factor could be race, religion, age - anything, it doesn't really matter.
I've recently been struggling with the notion that, as a 22-year old who is about to graduate, I am to enter an economy and a system set up and controlled entirely by the captains of finance and government who allowed the financial crisis of 2007 to occur, and who have been unable to "fix" the economy through monetary and fiscal reform. This has pushed me towards the study of Bitcoin, a "radical" tool that traditional economists are quick to dismiss as a libertarian/anarchist fantasy. I don't subscribe to any political viewpoint - I simply see a broken system that has destroyed the lives of many of the constituents that it was created to serve through corruption and negligence. Bitcoin is just another tool, such as Quantitative Easing and Interest rate manipulation, that we could possibly implement to reduce the volatility of the financial system and remove some of its susceptibility to greed and corruption.
My interest in Bitcoin nothing compared to ISIS, the PLO, the Black Panthers, or any other minority group that was oppressed and decided to try and change a system that it found unfair and stacked against it. The difference is that these "extremist" groups use violence to fight their battles, because they see the alternative life of dying poor and oppressed as a non-option.
If we were to advance every civilization to a point where the standard of living was high enough and the measure of inequality was low enough, I think we could eradicate most forms of physically violent extremism. Mental "extremism" in the form of thought-experiments pushing the boundaries of the current system would continue, but to the benefit of society in general. Will this ever happen? Probably not.