Don't write every part of your adventure in advance. Unless you and your players are OK with some strong railroad tracks or agree to follow plot hooks, it's a recipe for wasted content.

That doesn't mean write an adventure or campaign, it means write an outline and the next session or three of content and then see where the party starts to go. A good thing to get in the habit of is ending a session right after a major decision has been made, especially if it pertains to traveling. Try to align the end of a session with the party's decision on what cave, cellar or town to travel to next. Then you can prep it as needed.