What is the difference between thanking and stewarding donors for their generosity? How does real stewardship create impact?

Whether you have the luxury of working with a robust stewardship department, or (more likely) you are personally responsible for stewarding your donors, stewardship is the lifeblood of what we do; however, far too often it is relegated to the end of the cycle of philanthropy, etc. What happens if you disrupt that model and start stewarding prospects before they are even giving at their highest capacity? How do we balance our work in active fundraising and solicitation with our responsibility to steward our donors? What elements are employed in excellent versus mundane stewardship practices? And what qualities are donors really looking for when they are being stewarded?