How do I avoid being too sales-y with my writing?

This one's easy.  Don't SELL in your writing.  Focus on providing valuable information.  The goal of your writing is actually not to sell.  It's to demonstrate your validity as an expert in your field.  Few people have the ability to close a deal with writing alone.  You need your writing to invite people into your sphere.  From there you have to find a way to relationship build, either through personal contact, blogging, vlogging, working on small projects, advising, etc.  Once the trust is there, selling happens naturally.  So spend your time giving away the information you have been working so hard to obtain.  Give it away for free over and over again and people will flock to your business in droves.  And some of those people will become clients or customers.  Some of them will work with you on small projects and some of them will work with you for years.  Contrary to what so many professionals advise, I say stop trying to sell and start trying to help people.  Make a difference in their life and they will pay to keep you around.  It's a fair trade.  The man with money meets the woman with experience and they trade.  So get out there and make yourself trustworthy by caring and affecting change.