Although personality conflicts, political differences, or something as simple as disagreement over how high the office thermostat gets set can cause friction, the underlying difficulty is often misaligned expectations. For example, John is not meeting Mary's expectations and he is angry about it. Never mind that the two of them have never discussed their mutual expectations to begin with!
When you expect something from someone else - increased sales, stepped-up performance, higher productivity, or more help with your workload - you set yourself up for the possibility of disappointment. Offices are full of subordinates, co-workers, and superiors walking around resenting each other over expectations they never discussed, negotiated, or agreed to. Subordinates, peers, and superiors become "difficult" when they stand between you and your expectations.
Subordinates tend to expect that you are going to somehow make everything right in their world. It's an unreasonable expectation, yet it came with your promotion. Subordinates complain about being micromanaged yet resent it when you don't give concise and clear directions. If you give concise and clear directions and they don't follow through, they may still blame you.
Your peers' expectations can also be unreasonable. Jobs and job responsibilities shrink or expand depending on the person and her appetite for work. The problem is that no two individuals share the same appetite for work. This variability sets the stage for unrealistic expectations among peers. If you expect all people to invest the same amount of effort in their jobs as you do, you're likely to be disappointed. Or, turning the tables, you co-workers might expect you to pick-up the slack when they cause a problem, without ever admitting that they caused it. If you complain, you are difficult. Just because your co-workers' expectations aren't reasonable doesn't keep them from resenting you. Your boss may expect you to put in the same 60 to 80 hours of work per week that she does. Or she may have unreasonable expectations in terms of your productivity. She may expect you to know how to do certain tasks you have not been taught to do. Often, resentment results from unrealistic expectations that are simply based on a lack of awareness.
The fastest and simplest way to deal with the resentment that arises from unrealistic or unfulfilled expectations is to confront it head on. Usually, people naturally take their resentments to friends, comrades, or anyone they feel will be sympathetic toward them. The one person they don't go to is the one they're having trouble with. And yet he or she is the only person who can offer a solution.
If you feel someone resents you because of expectations you've set for them - or you resent someone such as your boss or co-worker for expectations they've set for you - talk to them. Resentments tend to evaporate when they are discussed. As long as conversations about expectations remain constructive, most people become less difficult once they feel they know the score. Both of you can more easily accept what you do or don't do if you are up front about it.
But you must be the one to initiate the conversation - the other person is unlikely to approach you. Sometimes people get so frustrated that they give up. They may stop trying to communicate and begin to ignore or avoid you. Especially if you are dealing with a difficult subordinate, it is your responsibility to make sure that you are speaking each other's language.