You must be extremely charming and need to believe in yourself completely. I have worked with many different pharmaceutical sales jobs, and I saw the best and worst. The current work of sales that I have is as a regional distributor for a large corporation.
When I used to arrive at the point of sale, I would work extremely hard. I used to generate revenue even by making a cold call. This was nothing but hard work.
I was barely making my ends meet, and got frustrated. Because I had not taken any selling career course, the company asked me to improve upon my selling skills. I was never promoted to management level. Sometimes what appears to be a promising sales job is really a desperate position that will lead nowhere.
You should be aware of pyramid schemes - they are everywhere in the sales industry. If you're gullible, you can be the victim of someone trying to take advantage of you; making money with you and you end up being a slave in an impossible situation. If this sounds like it's too good to be true, it could be. If it seems that it does not work, do not wait to see if it is. Find something better, and then never look back.
When you find the right sales representative jobs, no matter how you work, it will end up well in the end. Trust your instincts - they do not speak a lie. Sales jobs require intelligence, but they also require instincts. If you can not trust your customers you will not succeed.