First, a large purchase is much more likely to give your prospect anxiety. "Large" doesn't just refer to money, either.
If a purchase will require major changes on the prospect's part, such as a department reorganization or big lifestyle change, he will probably become nervous at several points in the buying process. Patience is the best response to this fear factor. Rushing the prospect will just make things worse, so give him plenty of time and reassurance to help him pull through.
Second, every purchase comes with a few trade-offs attached. As a prospect continues through the buying process, he will no doubt uncover some minuses to go with the pluses that you carefully explained to him. Of course, the perfect product doesn't exist, and your prospect knows that – but knowing about the drawbacks associated with your product can still cause him anxiety. Again, patience is the answer. Also, you'll want to be very clear about the benefits associated with your product so that the prospect is fully aware that those benefits outweigh the drawbacks.
Third, if your product or service is something totally new to the prospect, he'll be much more nervous about investing in it.
Not only is it something brand-new to him, but he may also have concerns about your company's longevity and how well it will support the new product. He'll also probably have a lot of concerns about implementing this product. With this fear factor, any facts you can provide to back up your product claims will help. This might include third-party reviews, testimonials, scientific studies, newspaper articles, etc.
Fourth, if more than one decision-maker is involved in the buying process, conflict between those decision-makers can create a lot of anxiety. A variant of this fear factor occurs when a high level decision-maker suddenly appears in the middle of the buying process. Now the other decision-makers have to justify themselves to this new person, and that can create a lot of anxiety. Usually some of the decision-makers will support your product while others will be rooting for the competition. You can help by arming your supporters with as much helpful information as possible, including product benefits, return on investment, hard evidence that supports your claims, and anything else that occurs to you.
When one of these fear factors arises, it's highly unlikely that your prospect will come out and tell you about it. You'll need to watch for the signals that indicate your sales processes has come to a halt because of prospect anxieties. The most blatant fear factor signal is when a previously enthusiastic prospect suddenly goes dark. Without warning, you'll find yourself unable to reach the prospect by phone and no longer getting responses to your emails.
Other, subtler signals include a sudden return to issues that you thought had been resolved, anxious or stressed body language, a string of postponements or other stalling activity, and absurd demands that you can't possibly meet. Whether the signal is blatant or fairly subtle, you need to dig out the root cause and help your prospect move past his fear. It may be difficult, especially if the prospect is now ducking your calls, but if you can just get him talking that's often all he needs to get over his fears and get the sale moving again.