Second, set some goals for yourself in the coming year at work. Maybe take a class for personal improvement or learn a new skill you could use at work. Review these goals the first of every month and see how you are doing. Finally, consider that resentment is a self-imposed feeling. It's your reaction to a situation, not a fixed circumstance - like age, gender, race, etc.
People lose out in promotional situations every day.
Most accept what happened and, if they want to stay working where they are, simply move on with their work. Of course, if you decide this is too personal and stressful, update your resume, and start looking around at other options sooner rather than later. I will soon graduate college. It seems that this year the employers at career fairs and on campus interviews are not as optimistic at the number of college grads they will be hiring in the next 12 months. I am interpreting this to mean that students are going to have to search harder for jobs.