you do not need to wait for next month to sell bitcoin. you could sell it today, then buy it back tomorrow, and re-sell it next week. it is called trading. you seek to profit from every action you perform. make sure your selling price is higher than when you purchased it.
The price does not really matter to me as long as I can make a nice profit then I can sell. I never sell all my coins at once because there might be a chance that the price will go up tomorrow as well.