First, realize that trying to accurately estimate how much time something is going to take is akin to accurately predicting the future and that people who ask you to do it are stupid. Then realize that sales-oriented deadlines are the source of all that is evil. Then shift away from sales oriented software. Instead focus on selling existing features and new features on the roadmap have no deadlines, they're done when they're done. Then realize almost no workplace will let you truly do that because chasing the sale is all that matters despite the latest buzz word rhetoric. Then estimate enough buffer to give you a reasonable time to complete it without calling your abilities into question. Then finish it faster so you score points with management, but not every time because then they'll begin to expect it. Now you have leveled up in mind games, an unfortunate but necessary tool in the tool belt. Then hate on sales oriented software some more, rinse and repeat.