Sketchbooks are awesome! Each page is an opportunity to grow and as pages fill up they provide valuable insight for your creative mind. They're a stress free place to explore your creativity, have fun and ultimately to discover yourself.
If ever find you're in a creative rut just flip back through the pages of your sketchbook. Sketchbooks provide a history of an artist's creative journey. Use it to build confidence, recognize trends and fuel creativity. It may surprise you that the best inspiration comes from within.
The path to developing a powerful sketchbook is first to recognize that we all have good and bad pages. A sketchbook should chronicle growth not a series of failures, so it's important to push yourself to make each page a small success. If a page really isn't working out don't be afraid to take it out.
Go ahead now and look back through your previous sketches, pick out the consistencies within your work. Pay attention to how you use line and create forms, find the work you feel most confident with and compare the old with the new. Now just let it guide you and see what happens.
Need a place to start fresh? a good all around sketchbook to start out with is the Moleskine dot grid notebook, the dot-grid provides unobtrusive structure making it great for both note-taking/design and freeform sketching.