When I reviewed the page, there were 18 other answers to the question. There was nothing particularly wrong with them, but they just weren't transferable or scalable. They didn't answer the question of how sales professionals stay motivated as much as they answered how certain salespeople motivate themselves and how certain sales managers motivate others.
The most important thing to understand is that when someone must ask how to motivate their salespeople, they may not have the right salespeople!
The best salespeople don't have to be motivated - they just are - and it not something they have to do. Sure, they are goal-orientated. Sure, they are disciplined. Sure, they love praise and recognition. But salespeople who love what they do and love either the thrill of success or the sight of their growing bank account are pre-motivated. Think pre-washed or pre-faded jeans. They come to the table wired for it.
The real issue is what to do about those who aren't wired for it. The easy answer is to evaluate the sales force and, as part of that process, look for the data which will tell you who is motivated; not in general terms, but specifically for success in sales. Who can be developed and how much improvement are they likely to show? You may learn that you don't have the right salespeople in the right roles and may need to make some changes.
You'll also see this problem with veteran salespeople who have made a lot of money and have become complacent. Just because they have succeeded in the past, doesn't mean they will continue to succeed in the future. And did they really succeed in the past or did they make a bunch of money because they inherited lucrative accounts?
Change is the best way to motivate a complacent sales force. Send a message that they can all be replaced and that you are willing to make those changes.
Read more of my articles on sales force motivation.