Just have your house as you want it. We have just bought a house where the previous occupant came close to being a hoarder, there were few pictures in the brochure or Rightmove, always a sign the house is a mess. But it did not stop us buying it and two other people offered and later withdrew. But of course that affected the value. But if you want to have the house a mess and take the down valuation that is fine.
Apart from that get the house clean and tidy and relax. The majority of people who do not like your house will not like it for reasons no one can do anything about - because a particular room is too small or too big, that the hall is too big/small, that the garden faces the wrong way.
As for viewing, I did all our viewings and the estate agent was very happy with that. Ours was an old house with 500 years of history, I could answer any uestions viewers asked about the house, village and area. The estate agent always had a feedback session with viewers and they could say any uncomplimentary things they wanted to say to her. She then passed them on to me. There were very few - and again were usually about things that could not be changed, ceiling height in the study and hall, which were low, 2 staircases etc.
But the best thing to do is just relax, getting uptight will not help.
Do remember that the housing market is very slow at the moment and has been for the last 2 years. Your house may be slow to sell. We were on the market for 15 months before we got a buyer, when usually the old timber framed houses along our road were considered highly desireable and sold uickly. The house we bought was on the market for 18 months before we put in an offer.