Your first job rarely ends up being the last one for most people. Yet, even if the job you're trying to leave isn't your first one, it can be an intimidating transition to make. Financial responsibilities usually come up first when considering leaving your current workplace, and for good reason.
Making sure you can pay rent and feed yourself should be your top priority. Always consider your options carefully when you are contemplating leaving your current position. Though there are certain situations where leaving your current job, without a new one already lined up, may be helpful or necessary.
A Toxic Work Environment.
A toxic workplace is not always one where you are getting harassed or yelled at. It can be as subtle as your managers not listening to your concerns and issues, or not providing help when you ask for it. Overall if you are having issues in the workplace, you should be communicating these with your supervisor or manager to see if the situation can be resolved.
In the case of harassment or mistreatment, you should always reach out to HR, a manager, or an attorney to protect yourself. If you do speak with a manager, for example, and things are still not getting better over the next month, then it's possibly time to consider leaving your job. Staying in a toxic environment will deplete any energy you have to search for new opportunities and make you susceptible to performing poorly in interviews.
Ethical or Moral Issues.
This is not pertaining to the personal lives of your coworkers or managers, but rather situations and decisions regarding the workplace. Are all customers being treated fairly and properly? Are all employees being treated fairly and properly? These are the main guiding questions that should be asked if you suspect the moral or ethical integrity of those you work for or with. If either of those questions are answered with a "no," then your next step is to talk to HR or an attorney.
Even if you are not the one making violations, their activities could damage your reputation if you are not careful. Moral and ethical allegations against you or the company could affect your ability to get another job. Preserve your good reputation and remove yourself from a situation that could put you at risk, if this is the situation you are in.
Unable to Search.
Does work have you so wrapped up that you have no time to search for a new job? Or you think you'll have time, but, once home, you are drained and bogged down with all your other responsibilities. Always consider and plan for your financial needs ahead of time.
Although, if you know you need to find a new job and you're financially prepared, put your two weeks in. You'll still be working all or most of those two weeks, but you'll feel a weight lifted off you. Those last two weeks could still be hectic, as you get your tasks sorted, but you can go home knowing it will be over soon and you can relax. Once calm, then your searching can begin in full swing.
Unable to be Yourself.
Are you able to search for a new job, but once you get an interview you can tell that you are not completely yourself? Maybe, the underlying lack of energy, due to all that you are juggling, leads to you being nervous or a cardboard version of yourself. The difference could be that you aren't able to answer interview questions as well as you normally would.
If taking a day or two off to unwind and recollect yourself is out of the question, then you should consider leaving your current job. When you're feeling good and prepared, you're more likely to answer interview questions well and make a good impression with your interviewer. Since you've already started searching for new work, you will know how many opportunities are out there for you. If the pickings are slim and competitive, then consider taking medical leave for a few days to decompress from "work-induced stress".
When contemplating leaving your current job, remember that it is ultimately your decision. If you are experiencing one of the situations detailed above, and you decide you need to remove yourself, do it. Put in your two weeks, and feel relieved knowing there's an end in sight. It is helpful when your family and friends are supportive, but if they aren't, you are the one that knows what is right for you.
Don't take this decision lightly. Talk to your manager, HR, attorney, family, and anyone else you see fit when making your decision. Make sure your finances are in order. With those squared away, then make your final choice. You will get through the rough patch, and you will find a new job.
Do what you've got to do, and may good luck be with you.