Self
A large part lies in the fact that with time, our interpretations change. Our self-image changes. Our patience with people and their shortcomings come down. Our happiness becomes more dependent on external (sometimes tangible) factors and less on ourselves. Our idea of introspection is to justify our actions and thoughts and come to the conclusion that there was no other way to behave, rather than give the benefit of doubt to the other person and bring down our level of discordance.Introspection has lost it's place in our life as calming oneself down is seen as a weakness. "For how long can I and should I calm myself down?" has become the predominant question in everyone's mind.
When we were young, we did this all the time and others did this to us too. As we become mentally and financially independent, this tendency goes down. We term it growing up, whereas it actually becomes a counter-productive loop which tends to mar our future self-growth as well as professional growth. This one thought of "For how long can I allow X to happen?" is the poisonous root of disruption.
I am not saying all disruption is bad. Some disruption is desirable too. Moreover, disruptions have been taking place all the time, even when we were young. It is the impatience which is a deterrent to healthy growth.
The issue with us today is that we have a threshold, a "patience bar" which is like the battery indicator on our mobile phones... which gets charged by a constant need to tell ourselves that at this age or this stage or after such and such, it is now enough. No more tolerance.
Relationships
Parents, which seemed like dictators when we were young, slowly start seeming like villains who want to control your life.Siblings fights, which were more frequent, more open and superficial, slowly start becoming "incidents" which start leaving deeper scars.
Friendships growing apart and withering because one or the other forgot some dates and events.
Intimate relations, like marriage, not able to bridge the gap between the person your spouse are... to what you want each other to become. No matter how much we try to deny it, we all want our spouses to become a newer, better, improved shadow of ourselves. More importantly, someone who has no emotional bonding with the life they had before marriage.
Inter-connecting relationships and changing dynamics of family setup, like marriage, children, which act more as a jolt than an enabler to growing up. Even small incidents being interpreted in so many different ways, often leading to discordance.
Social Media
Not social media, no. These factors don't create dissonance. They help to accentuate what we already think. We tend to seek affirmative information on the internet. Unknowingly, it creates a thought loop wherein we solidify our thoughts and term it correct. Worse, we might call it reality.We might argue that social media actually gives us more information and helps us to grow up. I disagree. Think about it - were you more patient in general when there was no internet to while way your time or are you now?
You had more things to do, time to think, tolerance for disagreements, inclination to understand the other person. You had a better vocabulary to express yourself. Proof -- the fact that you can express yourself well was developed when there was no internet. Compare that with the vocabulary youngsters have these days, when they are exposed to the internet at a very young age.