how to establish confidence in buying and selling altcoin because when looking at the price down and immediately want to sell even loss
You don't have to do that because in Cryptocurrency most of the coins that dumped all pump back higher than you bid so you don't lose anything but time for waiting.
Before you invest an Altcoin make sure you're confident in losing the amount because not all coins are rising up, and most of them will take a lot of time to recover.