The assassination business was a highly dangerous one. It was very likely they would not wake up to see the sun tomorrow, and it was because of this exact uncertainty that many low-tier-assassins picked up bad habits such as drug abuse, gambling, and lust.
On the contrary, a real high-tier-assassin had none of those bad habits. This was because they knew very well that one mistake was all it would take for them to lose their lives.
Shadow was only a Tier-Three Assassin from Quicksand. Although he was not substandard, he was certainly not the best. In Quicksand, the assassins were roughly divided into five tiers; Tier-Five was the worst, and normally meant trainees who were new to the organization. Next were the Tier-Four Assassins who had just gotten on track. As for Tier-Three Assassins like Shadow, they were merely considered experienced members.