I have a wonderful strategy for this case. Say, you have 10 BTC (or any other amount of any other currency) and want to increase your fiat funds. Means, you aren’t fanatical crypto geek who doesn’t accept fiat money at all. Thus, you should look at market and check price changes. When prices go up for at least 40%, you should sell a half of your initial capital – 5 BTC. When prices go down, you should do the opposite thing and buy additional coins, half of your capital. When prices are stable, it’s enough to continue spectating. This system isn’t ideal but it balances all possible risks, so you will be in plus, mostly.