I am not sure what the person in this house was saying NO to, but part of being a good photographer is knowing when to say no. No to taking an image, no to processing an image, no to the subject matter and no to some sales venue. Why do I say this? Because we are finite. We don’t have infinite time and resources. And as one photographer I respect put it, you just can’t shoot everything.
What this is all about, is becoming a more mature and refined photographer. Hopefully over time, if we critically evaluate our work, we learn not only what makes for a good photograph, but what doesn’t. We pass on shots we might have once taken. Maybe we need to wait for better light, the subject just isn’t that strong, or there isn’t any way to create a strong composition from the elements. In reviewing our images, we learn which ones are worth saving/processing and the ones that should be deleted (so hard to do). Maybe a sales venue consumes a lot of time with little in the way of real sales (low return on time invested).
I suspect learning to say no is harder when you don’t make your living from your photography. Because if you do, you have to learn to make the best of your time. Learning the discipline of saying no might make or break you.
Now does saying no mean you don’t take risks, try new things or explore new opportunities? No, just the opposite. The time you saved should give you some of the time you need to explore new things.