Some people just are better at changing their doing-hat to the editing- or evaluating-hat in a rapid fashion than others. Being (and staying) conscious about this is already 80% of the solution. However the real reality check is always when you have a room full of people look at ghe thing you made.
If it helps, try to make rituals around the reflection part. Be it something simple as putting your hands into your pockets, making a cup of tea or showing it to a friend. Everything that gets you away, everything that makes you explain it to aomeone else etc. will help.