How do I handle timelines that everyone treats as promises?

You can plan any project to completion, and you have learned the quiet trap that comes with it: an estimate you offer gets remembered as a promise you made. A timeline is your best honest guess about an uncertain future, but people hear a guarantee. Carrying the gap between those two things, again and again, is genuinely wearing. Change how you hand over the timeline, not how well you plan. Give ranges instead of single dates, and say plainly what they depend on. Name the assumptions out loud, so that when reality shifts, everyone can see why the date shifts too. This is not hedging. It is teaching the people around you what a plan actually is, so they stop mistaking a forecast for a vow. And release the guilt you did not earn. When you planned honestly and the world changed, you did not break a promise; the future simply did what the future does. Do the careful work, communicate the uncertainty clearly, and let go of the rest. You are responsible for planning well, not for making the future obey your dates.