I am not the same person that I used to be when I migrated from my hometown to Delhi. I've changed. I used to be a shy, self-conscious, opinionated, rigid and determined nerd who had an opinion about every single thing in this universe, who disliked things which didn't fit in his rationale. Now, I'm sort of detached to majority of the things in this universe. It's not that I've stopped caring, it's just that I've regulated things that I care about. You may call that I've become selfish.
Being selfish has its own pros and cons. It makes you focussed about your ambitions, but at the same time it makes you indifferent to majority of things which others think should bother you. The end result is that you unconsciously might end up hurting people - not by doing anything, but rather by doing nothing. Initially, people expect you to respond to things that you're indifferent about. But when they don't get the desired response, they feel bad and stop expecting. You get what you want - no expectations from you and they get to know what they should expect from you - no response. The end result is a different kind of freedom, which seems solitude at first and becomes loneliness later. Because when you come out of your ocean of self, you realize that there is nobody around to share your 'self' with. Your indifference becomes the cause of your desolation and thus, indifference gestating inside you gives birth to its offspring - depression.