Thanks folks 
Well Saadia, I do miss the one or two people I became close to at my old job as I was there for just over 4 years so I intend to stay in touch with these people but other than them, I don’t miss anyone else to that level. I guess the reason is that I have always seen a workplace as exactly that–a place where you go to “work,” to fulfill career objectives, etc., not to necessarily foster long-lasting friendships at. In addition, my field allows for very minimal relationship-building with employees (other than perhaps those in HR itself) for reasons related to conflict-of-interest. Mind you, there is plenty of interaction with company personnel on a daily basis but HR is expected to keep a safe distance from other employees by definition. I think this applies to any HR department of an organization.
I think it is great to develop your skills, utilize them, and move on to something better where newer skills can be learned and applied. Basically, a career is a ladder of sorts that one is constantly climbing until you don’t have the drive to climb any further. By transitioning into newer, better opportunities, you enhance your skills and keep yourself ahead of the competition; hence you become bolder and more confident in yourself. Besides, the feeling of achievement each time you take the next step up is incredible.