You did a big mistake because you bought them at very high value and now you sold them for loss. Really you made a big mistake by selling them at the current price, so in crypto, you need to wait patiently until price starts increasing again.
I agree, never sell for less than you bought, if you do it means either the project was crap and you should have known better, or you invested money you couldn't afford. I'm holding coins that have dropped 60-90% but most are actually doing really well on tech development, marketing, adoption etc, so holding now isn't keeping me awake at night. Good projects will survive this market!