Frustration at workforce

There is a management level position (not manager position) available in our group in Nov. and I applied for it. Before the position posted, my manager called me and asked if I would like to apply for it – a very good sign when she asked me and I also agreed to take an EXTRA task to cover that position.

After a while, I did not receive any response about my application. Today, she called me to have a small talk – she offered the position to someone else already. I was so shocked and felt so bad that I have been used my manager. She is the one who initially approached me about the position but then without any sign, she offered to someone else. Unfortunately, I told her that I don’t have any problem with the arrangement as far as she gave me the clear picture. – What else I can say? I won’t trust her anymore in my heart but I will have to stay with the co. for a long time (government job).

I would like to hear from you guys here if you are in my boat, what is a better way to deal with this kind of office publicities rather than take seriously and personally. _:'(

Your advices are highly appreciated since I was so disappointed!