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.
Yes, the best way to overcome a fear of holding your coins is to forget about them, get busy doing something important like working on a campaign or working on your own personal project. I recommend checking your HODL coins in 2-3 weeks. Checking your coins 2-3 times a day will make you panic and that may lead you to sell at lost. For me, I basically HODL for an average of 6 months, if it works out fine and if it didn't I'll just wait for another 6 months.