Business is a mixture of good marketing, finance accounting, having the right people and a small bit of luck. But most of the work is done by careful planning. For example in your case. Think about your previous customers and think about why they bought these books. You are likely to find a pattern emerging and this pattern is always the same which ist, demand. You supply they demand you give it to them they hand over the money. Now you need to find out what triggers that demand and try to trigger it with them again to purchase your current products or find new people who have similar demands and advertise your supplies to them. It sounds a bit theoratical but the concept of trade is the same. Now there is of course a cretain level of luck involved but with normal trade it is always a matter of good planning, knowing who you sell to and then achieving maximum product satisfaction by finding the perfect supply for the customer demand.

I think business is to be done after a good experience. At the beginning we should start by observing other businessmen. Maybe by working at there shops or just observing them. Business is also a bit of luck. So if fell that your luck is over and you cant do it anymore so leave it and focus on your studies and think about something else. Good luck.

No. I think good business depends on good planning and good management.

Obviously you have gotta be selling a product/service that 'people' want/need.

Set-up a toilet-roll company. Everyone needs that!

just change the way that you are using for selling, then you can see changes

I am 19 and I start make money by selling second hand reference books to colleagues. At the beginning of two weeks of a semester, I was able to earn $400++ dollars in a two weeks time. However, it starts to get lower each day until today that I can't earn any profit at all. I feel very disappoint that I have a few thick books now and yet can't sell out at a good price. Is that my luck is over? Should I switch to sell something else? should I stop and focus on study?