1. Your chosen affiliate marketing program makes you buy the program first. This is not uncommon, and in reality owning the product you are going to sell is a good idea.
What happens in many cases is that the affiliate marketer does not make money in the early days, looses confidence, and drifts to the next available "sure thing'. Over a period of time this can add up to a substantial amount of losses.
The moral of this story is to always promote your product, until at the very least you recoup the cost that you spent for it. If you know anything about how to market online, this should be achievable.
2. Your income does not exceed the amount of money you are putting into advertising. Often this happens when advertising online, particularly if the marketer makes use of a pay per click campaign.
The best way to avoid this is to start with a small campaign, and get a real number in your mind in terms of how much money you must spend before you are creating a sale. Then you can calculate the cost per click, to determine whether you can bid more or should bid less.
3. Your judgment of the value of your time and effort will improve as you build your experience and knowledge. You will discover that the best marketers online are very aware of the value of their time.
The key point here is that you can spend time every day that is not productive as an affiliate marketer. Once you have everything in place to promote your product, you should spend the majority of your time actually working on marketing and advertising.
Getting visitors to a website is really the only way you are going to sell anything anyway. Many affiliate marketers do not spend their time wisely, and it ends up costing them in terms of productivity and profits.
In summary these are three ways to lose money with affiliate marketing on the Internet. There really is no excuse for this. Your income levels can be influenced by your actions and decisions, so take careful care to monitor your business costs each month, and develop a professional attitude in your online business.