For me the most important thing is to consider every piece of feedback fairly. It’s easy to dismiss a suggestion because I don’t think it will work out. But taking it on as a challenge — “Hmm.. I wonder if I’m skilled enough to make these hot pink zebras stripes work…” — can often be more rewarding. So, don’t be lazy — just try stuff, even if you think it’s silly. You might surprise yourself.
The other thing to remember is that there is a lot of play when it comes to designing pragmatically. There may be a study showing that Helvetica is the most legible font for headlines. But if you use Rockwell instead, is the business going to go down in flames? Doubtful. Be knowledgeable about your craft and share that knowledge. Fight for what is right, and pick your battles.
I could expand more specifically with examples in another post if you would like.