If you don't want to lose profit, then never sell currency for price that is lower than price that you bought coins, as this way you won't lose it
And sell only when price is larger than price that you bought them, and try to buy coins when they are pretty cheap for largest profit
Good strategy. I have been keeping a bunch of alt coins myself into paper wallets for future reference. It will serve more like a savings account than a checking account since it will be only used in case the price goes above the one I have initially bought the coins from. The most profitable coins for me have been PoS coins, although I have to admit that it is very tricky to receive good rewards (stakes) if you don't have a huge balance of the coin. Also, the difficulty is another factor, but at least I am making extra coins with these (which could be seen as earnings).