In enterprise sales situations (less so, for consumer-facing businesses), it's important to remember that there are multiple people (and/or business units) in the enterprise customer who will have different, and often contradictory, points of view about whether the customer should buy your product.
An important, often forgotten, lesson for entrepreneurs is to remember that one of the most important things you can sometimes do is to help some employees of the customer company make their case for buying your product to their superiors, as well as to other business functions, like the office of the CFO, whose job it is to "screen" all such purchases (in not a few companies, sales-related employees (sometimes unfairly) refer to the General Counsel and/or CFO as the "revenue prevention departments").
This nuance -- that some employees of your "customer" are, actually, your sales "allies" against other employees -- is very important, but easy to forget.
The reasons are varied (and some of these will be "personal" (e.g., some employee involved in the product or service evaluation process just doesn't think your product is as good as competing products)), but the important one is "institutional" and lies along this main dimension: "What Do You Get Blamed For?"
Most enterprise products or services are aimed at improving some specific, identifiable business function in the enterprise customer: e.g., CRM is aimed at helping customers improve their sales processes. So the employee (here, say, the VP Sales) who will use the CRM system wants the company to buy it because it will help him do his job better.
The VP Sales wants to spend money to get help because he gets blamed if the company's sales targets are not met (but, importantly, not not blamed if the company's costs are not properly controlled).
For the CFO, it's (almost) the reverse.
The CFO gets no credit for achievements on the revenue side of the business; that glory goes to the VP Sales. The CFO, however, is ("institutionally") focused more on keeping costs down because he gets blamed for anything that goes wrong on the cost side of the business.
While my example is, of course, an oversimplified description of the more complex reality inside any enterpriese customer, it's still easy to see that some employees in the enterprise customer will want to spend money on your product (e.g., you're selling a CRM system to the VP Sales) and some will want to make sure that as little money is spent as possible.
The lesson: part of helping make the sale is treating (in my example) the VP Sales as your ally in a "struggle" with the CFO over the purchase of your product.
Seasoned, smart sales execs in large companies know this lesson very well, but it's not something entrepreneurs in startups always consider.
But, it's important (often decisive), so they always should.