Changing Jobs may be risky but if you plan it well, it will serve your purpose. You should not make the mistake of resigning the job and then start hunting for a new job. If you have decided to quit the current job then start hunting for a new one. Once you get a confirmation from the new employer and you are confident that the new job is better than the current one you could resign the current job. Why do people change jobs? The answer would be variable from one person to another. Let us discuss some of the common factors that lead to changing Jobs.
If you feel that you are not being recognized for your work or there is no growth in your company it is better to speak with your superiors and find out if there was anything wrong with your performance. You can switch your career either to a new company or some other industry if you have the skills.
All jobs are not fit for everyone. Some jobs may be hazardous and some may be stressful. If you think "this is not a cup of my tea" try changing to some other job. For instance if you are working in night shifts and feel your health is getting deteriorated try switching to day time jobs.
You are not happy with your current job. You think you can excel in some other industry. You hate Mondays! Yes most of the employees who aren't happy with their work place are happy during weekends but when it comes to Monday they hate going to office. You think your job is monotonous and a boredom. If you are influenced any of these thoughts try to switch to a job or different industry which you may be interested in.
You are working in the current firm for so many years but still you don't get the "Supervisor" post even though you are well suitable for that post, try applying for jobs in some other company based on your experience and goals.
Your company is not doing well in terms of finance. In effect to this there is no pay hike for this year or pay hike is meager compared to other companies in the same field. It strikes the alarm of changing jobs to some other company.