I only feel envious occasionally, and that's usually about famous people, because I know the money would make my life a lot more comfortable. However, that goes away when I remind myself of the effort famous people usually put in.
Following some down-to-earth people on Twitter opened me up to seeing what these people do every day, and yes they get paid a tonne and live a great looking lifestyle, but usually they are way busier in their day-to-day life than I am. There are also a lot of downsides people don't consider, which I think about too. Then the envy goes away or I get bored obsessing over it.
I do also feel what you are saying regarding people making connections without you. When I started a new job, I could see and hear conversations I was not part of, wanted to be part of, but didn't know how to join. It made me sad to hear two people whispering about something and not be included. But that is how life is, and I think there's a maturity that comes with accepting that the conversation over there does not include you, and you should get on with what you are doing.
The only way to get rid of the envy or jealousy is to accept it and move on. Acknowledge what it is you are wanting, if you can get it, then take the steps to get it, and if you cannot, then move on. The negative feelings only affect you, no one else, so you can choose to let them go.
Make the effort to go out now that you are on break. A lot of people will be willing to socialize, but unwilling to be the instigator. Text people and catch up over coffee, organize going bowling, take control.
But keep in mind that to be a comfortable and secure person, you need to be happy alone, and not need other people to be content.