The big lesson I try to pass on to everyone. Don't ever assume you will have a job next week. Be polite to any headhunters, assuming they are the professional kind, keep your resume up to date, network like crazy, have a few side project plans, don't be afraid of small jobs on the side, and most importantly keep a 3 - 6 month emergency fund. That fund doesn't have to be what you make in 6 months, but at least what your bare bones expenses are (mortgage, utility bills, minimum credit card payments), and try to keep your have-to recurring monthly expenses lower (mortgage / car payments, etc). That doesn't mean you can't spend on extra stuff, just make sure you can cancel them at any time.
You are most likely an at-will employee. You or the employer can terminate the relationship immediately giving any reason or no reason. Just have money saved up and don't be afraid to quit without notice to something better if you need to.