You've come to the conclusion that you're in the wrong career.
Perhaps you made a mistaken choice early on ("I went to law school because I wanted to go after bad guys. I didn't realize my advancement would be primarily about taking lengthy depositions,racking up billable hours, and brow nosing the partners").
Perhaps the field you chose has been so transformed by technology that you no longer see a promising path forward (publishing or printing, for example).
Perhaps a tragedy in your life has caused you to reexamine your priorities ("When my younger brother came down with terminal cancer I came face-to-face with the fragility of life and decided I was going to live life more meaningfully").
Or perhaps you're just burned out ("Advertising seemed so glamorous at first, but the constant crisis atmosphere and pressure have worn me down").
There are two primary paths to career transition. The first involves moving into an occupation relatively closely aligned to the path you've been on. Moving from working in financial accounting to government financial regulation, for example. Or from public relations to lobbying. Or from computer programming to IT consulting.
This kind of move involves 1) taking stock of your strengths/skills and then determining what kinds of careers would utilize those skills*; 2) ascertaining ways in which a new career would be different from, and better than, the one you are currently in. Less stress? More variety? Less boredom? Higher compensation potential? More flexibility? Less isolation? Which of all of these factors are the most important ones to you? Finally, 3) identifying the kinds of unique experiences and perspectives you have that would enable you to make a real contribution, and creating a persuasive narrative about that.
The second primary path to career transition involves moving in a more radically different direction, a direction that at the beginning of the process is unknown or at the least quite uncertain. The way forward on this path can be frustrating, precisely because the destination is so ill-defined. There are two essential personal qualities that you must have, or cultivate, in order to successfully attain your goal of finding a new career direction: a willingness to explore many different avenues of information gathering, and patience.
I have blogged extensively about the absolutely critical role of exploration, and about numerous approaches to it (see:
Fundamentally, the more different sources you consult in order to explore, the more inspirational ideas (and the more information) you will have about your options).
As for patience, William Bridges, an expert on life transitions, notes that the vast majority of the time there is a period of uncertainty, a "neutral zone" as he terms it in his book The Way of Transition, that can't (or at least shouldn't) be rushed, and that out of which new ideas will emerge organically. Generally, a very valuable aspect of one's time in the neutral zone is to take time to "chill," allowing time and space for the mind to dream. Trying to rush through this zone, trying to force an answer, could be as fruitless as trying to get a tulip to bloom before its winter rest period is ended.
Be prepared for the fact that, whichever of the two career exploration paths you choose, there will probably be doubt, fear, and even occasionally hopelessness, involved. That's natural: few of us are very comfortable moving into the unknown. Having a professional partner take this journey with you can be invaluable, urging you on, suggesting alternatives, helping you evaluate options. But whether you choose to work with a life or career coach or not, know that millions of people have moved down these same paths, often with great success.
* What Color Is Your Parachute" has an excellent set of exercises that will help you determine your transferable skills.