The guest list is generally a working document for most of the planning process. If you feel like it's never finalized, your not alone. The key to staying stress-free is managing it properly and making notes, even of those "I'll remember" things. During wedding planning things are generally more stressful and you're more likely to forget. Let me tell you a bit about my experience and how you can learn from it. I started as most do with a list from each side of the family, and no different from the norm some of the lists had some odd additions. My husband and I discussed why my his first grade teacher and some others were included on the list, but didn't make any rash decisions on cutting people. Eventually we sent out save the dates and continued on with our planning. When it came time to crunch the numbers and determine number of meals, space, and invites I couldn't remember who I sent save the dates to. Did I send them to everyone... or just the people we were sure about?
How terrible would it be if I send them a save the date and the invitation never came . . . yes probably the worst. So as a result everyone got invited.
Everyone works in their own way whether they prefer paper lists or electronic but my best recommendation would be to use a spreadsheet to keep your guest list organized or better yet Google Sheets so that anyone can edit at any time from anywhere! Download the Guest List Planner Organizer. It's set-up with all the important categories of information you will likely need to collect about your guests, including columns for sending save the dates, invitations, and thank you cards. It's also fully editable so you can make it your own. No matter how you're managing your list, don't let it take advantage of you!