1. taking more than required time in research of domains, specially whenever good domains are available for hand registration or godaddy closeout auctions, i'm like are you really sure these domains are worth and if they are worth why are others not regging up, then after few minutes i notice those domains are gone and listed on sedo or other martketplaces for $300-500, few times even $1K+ there is a reason for me taking time because i used to register lot of unworthy useless domains initially without thinking much, i need to find a balance between this , neither registering quickly w/o giving a thought nor taking too much time for it and going in deep research.
2. Letting go away lot of cheap 5N .com domain offers for low price. i was like who the fuck will care for these numeric domains, didnt had any idea about chinese domainers.
3. i had got offer for one domain $1000 and that email went to spam, i noticed it after few weeks and believed it must not be a genuine offer, then after few days i somehow decided to reply to that email to later realize the guy and offer was genuine, he needed it quickly, after waiting for my response almost a month, he just bought another similar domain for $2000+, only 2 days before i responded, he said he would have given me upto $1500-2000K like he paid to get similar domain, the best offer i have got after this for that domain is just $80, i wish i should have replied him when i had seen that email.
4. this is quite silly but i usually forget to put coupon or correcting the registration period of 5 years which is automated in lot of registrations like godaddy.
5. Time management