New co-workers are an expected reality. When we change jobs, we suddenly have a group of new co-workers to get to know and get along with. Yet even if we stay at a job we still have to adjust to new co-workers when old ones leave or the company grows. Adjusting to these new workers may be especially difficult if they have trouble fitting into the company culture.
If you're firmly set in your company's culture and your new co-worker doesn't seem to be even trying to fit in, this could make things tense between you. Make an effort to pleasantly help him fit in. Show her the ropes and try not to judge the new hire too harshly. Remember what it was like when you started in a new firm, but at the same time consider that this person's experiences and abilities may be different from yours.
Another cause of having difficulty adjusting to new co-workers may be your relationship with the person that used to have the job. Even if you weren't friends or even particularly close as co-workers, you may just have grown used to how that person did his or her job and how he or she interacted with you each day. It's amazing just how much of a habit our workdays can become to us if we're not consciously aware of it.
A common cause of not adjusting well to a new co-worker is getting used to what we may see as their annoying habits. We may have finally been able to tune out our old co-worker's loud phone calls or habit of interrupting us constantly only to find that the worker that has taken his or her place does something that annoys us even more! Ultimately, we need to focus on our job goals and not let any annoyances with co-workers get in the way of developing professional relationships with every person in the company.