Sounds like a contradiction right? Well it isn't.
You never know when the opportunity to sell will present itself. The best course of action is to run your small business like a a buyer will determine how much they are willing to pay you for your business tomorrow. Run it well, do the right things and have all your books and records in excellent condition.
But...... then why run it like you'll own it forever?
Because you can't out guess what a particular buyer will value. The best you can do is, as always, do what's best for your business.
Your decisions and actions as a business owner will determine what your business is worth, tomorrow or 5 years from now.