I had always thought I had high self esteem.
I would like to suggest..............honesty.
I think it is very common in the workplace to feel insecure and even inadequate- I always do, especially in the very beginning. I mean there are so many different personalities squeezed into one single environment, situations arise and conflicts happen. I have learned many valuable lessons in the workplace, I still need to find the time to write about them on here.
My advice is to kind of take things slowly and observe, observe, observe! Who needs to rush into happy hours and alliances when you're still getting to know everybody. And trust me, those happy hours are not always so happy- -they fuel gossip and you don;t need that right now. :)