Defining the scope
This is often a tough part for designers: knowing and defining the scope of a project. It's usual for projects to last longer than expected, but this should not be a problem, as it leads to more work. But, sometimes, clients' expectations and your expectations are not the same, so it is best to set boundaries to prevent unexpected work and scope creep. Putting everything in a contract will help you. Here are some templates that you can use: https://www.smashingmagazine.com/2013/04/legal-guide-contract-samples-for-designers/.