Hi The Millster!
How about taking a nice break, doesn't have to cost you anything, or go abroad and have "time out". I did just that, even for a month, when I was made redundant, well its a long story but was forced to leave, due to stress too!
Have returned, and feel relieved that I;ve left a company that does NOT treat its employees well! You are a bright individual, and have more to offer a company, and seek out Employers that treat their staff well such as John Lewis for e.g, I don't know what went on for you, but just taking the break, and writing down what you want to do (if money was no object) what you enjoy doing, and perhaps developing a hobby/passion that makes you feel good! You are very young, and have alot of options open to you. I am 32, and don't really think I can go back into education really, so I am thinking of become a driving instructor, as thats something which closely resembles what I did before and I enjoyed it!
Think about what aspect of your job that you enjoyed the most? was it the planning and organising of diaries/people - then maybe you would be fantastic at being a Party organiser/Wedding planner? Brainstorm your dreams, anything that you have ever done to this present day, write it down - and ideas should come to you!
Also, read books if your into that sort of thing, visit Careers guidance seminars, seek a advice from Employment Agencies, friends and use these sources of advice to help YOU make your decision.
I used to work as an Employment Advisor, and carried out Fraud work to Managerial, I loved the Advisory part of it, so I'm planning my future like that.
Finally, have fun when you do this, get your friends together who maybe in a similar situation as you, or your best mate someone wise, and think whats really important to you, money, or a good career/job satisfaction, or both, etc etc.
I hope you find what your looking for,