For many years, I owned a successful home-decor store. I loved helping my customers. Often, they would come in looking for something in particular but be distracted by 'bright shiny objects' and end up leaving without making a purchasing decision. So I learned, it's important to keep a focus.
So my question is .... are you distracted by shiny objects? Or do you have a true focus? How do you make decisions in your business? Are they based on budget? time? etc.? What if you had a clear, written business vision statement and you based all your decisions as to whether they were in alignment with your vision -- this would make decisions-making much easier!
The same is true for marketing! Don't get distracted by the newest & brightest shiny object. Have a goal - a focus and base your marketing decisions against it. Decisions was to where to start, what marketing tool to use, etc. will become MUCH easier.
So Reason #4 why marketing is so difficult --- lack of focus! Pretend marketing is a road trip -- what is your G.P.S.? Do you know your Goals, Perfect Client, and Strategy? If you know these 3 things, it will keep you focussed and your marketing will be successful!