I Need To Vent A Little

We often hear others say we should lower our expectations of the people in our lives. Is this possible? If so then why am I struggling? I don't go around expecting too much of people but somewhere in my busy mind I think common decency, kindness, gratitude and selflessness is not much to expect of others. Here's the thing, I have recently been promoted at work. I was taken by surprise but I gladly accepted because I know I have earned it. The promotion is a huge leap from my previous position. There is no doubt in my mind that I have big shoes to fill but rest assured I will take over and continue smoothly.
The part that upsets me is that, from a staff count of just over 50 people only 3 of them has congratulated me, 2 of which are my seniors, the other a good colleague. So I feel a little disappointed but I convince myself that it's just me over reacting. The part that makes me sad is that none of them speak to me now, if it's work that needs to be discussed yes they will but no small talk or office humor. Why should things change? I can't just ignore the awkwardness and keep doing my job because I will have to work closely with majority of these people. I have been promoted to management level but that doesn't mean this changes the person I am. This promotion made a difference to my bank account also upgraded my title but I'm still me. It baffles when I try to make sense of it all. This is something I worked so hard for but right now I am not happy, I just don't feel good, like the way I imagined I would.