1. Do not remember electronic wallet password
2. Do not back up your wallet
3. Do not research new services
4. Buy and sell based on feelings
5. Leave your money in the electronic money floor
6. Waste time on faucets (we all did)
7. Collect dust and pay high fees on it
8. Leave coins in an exchange
9. Trust the wrong people and get scammed
10. Panic at a price correction
LOL, agreed with sixth one. We all have wasted so much time on these faucets to collect the small fraction of bitcoins. This is how everyone started and learned after experiencing these mistakes.