Re: Can I Do That ?
i find that characters want to do this a lot - they always want to escape from their story and from their author and have a life of their own.
which isn't a bad thing in itself, but it can harm your writing, as you are finding, and i think you may already have touched on one of the answers.
if you know what kind of adventures your characters will have outside of your main story, make notes for each character or each group of characters. if the adventures are neccessary to the main story, include them in the main story. if they are not relevant, leave them as notes and come back to them later, after you have finished your main story,to give your audience more about the characters they like.
Tolkein did this (sort of) in LOTR - the story of Aragorn and Arwen isn't in the main text of the book; rather, it is included as an Appendix at the very end of the book.
hope this helps, chap