First of All, Your Question Can be " Whats Your Worst Experience In Crypto"
Lets Move toward the Answer, Peopel Uselly Says That Hold Is Gold , Actually Not Just Other Peoples I also believe In Crypto Hold Is Gold, But In The Last Btc Dump, It Was My Worst Experience To Hold And Not Sell On Top, Mostly Alts Reached to new ATH , and My Portfolio Was  also contain Many Alts , But I Can't Book Profit and hold and hold, and Suddenly when market dump, my portfolio almost gone to 70% loss also i don't have any BUSD or Usdt to take dips entries, so it was my worst experience in crypto. And Now Everytime I am Trying To Book Profits and hold some for long term.