Some time your product provide you very high response in beginning and with in days come very low . Give any two reasons.

If you mean response from the customers:

Products have a life cycle, at the beginning the demand is increasing, but after a while it reaches stability and after that it starts to decrease. The time of each stage depend on the product, the market and your marketing activities.

In21st century profession and perfection matters, and products outdate much faster than old days, so we always have to keep and eye open and move according to Market's demand, improve the quality and appearance of the product more frequently. So1- Selling the same product without watching the competition can cause the decrease in sales.2- A product must be accessible for most ages, and if it is made to be used by certain people, the market exhaust fast and the sales will go down.3- It is also important to know how to advertise and where to sell your product, the supply should never exceed the demand.

may be your product is going to damage in short time or may be other company is give the same think with low price 

because one concider that he has done his job so he does not concentrate on his work as in start