Simply forget about your coins. Stop to read any news related and stop to check the price daily or 2-3 times a day. You will have less stress and so less fear of your coins. Do it at least 1 month and you will see. 1 month is nothing in a life. After a month just do your usual stuff once a week, check the rate, read some news, ect, close everything and keep rolling the life.
Easy said than done especially if this is the only thing you do in life. I think the most practical way to minimize regret or fear on holdings are to maintain two accounts for cryptomarket; One for trading and also one for investing.
Investing or long term accounts will be maintained by continuously adding value overtime. This will protect you from fluctuation because you are doing the cost averaging by acquiring additional funds during bear market.
You will still maintain the trading account for you to reap the benefits of volatility, acquiring the coins at low price then sell at it high price. These two strategies I think will answer the OP's question.