@Ann72
I don't always start off with a complete picture of what I want to do with a space, but I very much know what I like and am quite good at finding it within my budget. One I have decided on one element, the rest usually just falls into place.
When I was doing my new bathrooms, the builder repeatedly tried to talk me out of using the tiles I had chosen for the downstairs toilet, but I stuck to my guns. Everyone, and I mean every single friend, family member or guest, who has seen that room absolutely loves the tiles. They get more comments than most things in the house.
Some people know what they don't like, but have no idea of what they do like and therefore veer on the side of caution. If you try to make suggestions, e.g. colours or whatever, they can't picture it. I usually tell them to look at interiors magazines and at Pinterest as a picture speaks a thousand words.