Unfortunately, in this market, that is one of the uncertainties that you should bear and carry. Market assets, even the strong ones, always have the volatility feature that could affect its price to go up or down instantly, thus, having to dream of a constant amount would be next to impossible, especially if you follow a constant trading rate and strategy, and if you also trade for the same coins, you can achieve that if you would have a goal in mind that you would always want to hit; however, for that to have some semblance to being certain is still up in the air.