There are several reasons to leave your current job or career. Having said that, the reason that you ultimately choose is going to be up to you and how you feel about the change. Before you decide to leave a job or career, no matter what that occupation might be, one thing remains constant. That reason is to make sure you have the means to do so. In other words, if you don't have the financial means to quit your current job at the present time, you may want to think about keeping your current job until you have your new job, or reason for leaving that job ready.
Only you can really decide whether or not the reason or reasons for leaving a job are good in your particular case. However, there are still several reasons that drive us that we have in common with others. For example, one good reason for leaving a job is that you don't enjoy your occupation. This doesn't necessarily mean you have to enjoy your job, but you shouldn't hate it either. People who get into a career field that involves their passion, normally like their job more and are less likely to leave that job. For example, someone who loves fitness may want to become a personal trainer, or even a dietitian. Think hard about why you really want to leave your job, and if that reason turns out to be along the lines of not liking your current career, then you should really think hard about what it is you want to do.
Other good reasons for leaving a job include money, atmosphere, and family. You may like your job, but need more money. For example, if you are a pizza delivery driver and like delivering things, you might consider truck driver jobs. Even though you would not be delivering pizza, truck driver jobs can be similar. You can make deliveries while listening to your favorite music and being independent. Truck driver jobs also pay much better in most cases. If you don't care for your current job than you should look for executive jobs. Executive jobs are not always the most fun jobs, but they usually pay pretty well and give you the opportunity for career advancements. If the money and not the job itself is what is most important to you, consider an executive job.
Your atmosphere in which you work may be a good reason for leaving your job. For example, you may like the job you do and the money that comes with it, but you may not care for the people you work with or the conditions. If this is the case you can use free job posting sites to find a similar job. Depending on the job you currently do and the availability of similar jobs, using free job posting sites can help you find a similar job to the one you love, but one with with better working conditions and atmosphere. These days you can find more with free job posting sites than looking in your local newspaper in most cases. However, this doesn't mean you shouldn't check both.
Family is another big reason for leaving a job. Sometimes you have children or sick family members at home that you want to be there for. If this is the case you don't necessarily have to not work, or even quit your current job. Jobs at home are very popular these days. When you have jobs from home, you can normally work right out of your home office even with family members around. Many jobs from home will also allow you to work when you want.