Every once in awhile I run across someone (sometimes myself) who feel the need to reflexively defend a design against all who would try to "improve" it.
This can be terrible news for teammates, the design, and the people who need to use the product. It not only reduces the chance that the design can be made more coherent within itself and the larger system, it calcifies the response of the designer and undercuts the value of having a team.
That's why it's important to retain at least a small opening for feedback no matter how much we love our designs. Unless we're a lone designer and own the company, they never "belonged" to us anyway.