Hi Clare
As Jotommo above says a lot of it comes down to experience and confidence. To stay fresh you have to be motivated and INSPIRED. Look through magazines, art books, architecture ANYTHING and EVERYTHING creative to inspire you, and you have to keep on top of your training and education throughout your entire career if you want to try new things, looks, develop your techniques etc.
The more you learn, the more confidence you'll have and the stronger a stylist you will become. Buy a block head to practice new looks on and use them so you can get the best value for money on them (i.e. starting with longer cuts, working shorter) that way you have time to practice without worrying about clients time and mistakes. Its a really great tool for developing your ideas and techniques.
Have a look at our website too, there may be some looks on there you'd like to try or that may well inspire you to try other looks if you're feeling a bit "safe" at the moment.
It's great that you can recgonise that in yourself and its obivous you're passionate about it or you wouldn't care!
So best of luck and stay motivated!
MHD x x x x