A designers' job is hard. You are expected to deliver, but rarely get a seat at the table when the choices are made. It's easy to feel like you are the neglected tail end of the process, and in many cases this might be true. It might feel like no one will notice if you don't put in that extra 15% to make the work really shine. maybe no one will. The people worth working for will though.
Most design work that makes it into the world is 85% work. It's fine. It doesn't hurt anyone. It's not ugly. But it also missed it's chance to make a positive impact. 85% work will float you through a career, but 95% or 100% work will make you a star.