Near tried to call Mello every hour, but the blonde didn't answer the phone. And finally, Near realized he had lost.
This was the moment he decided to beat Mello at any price.
It was the moment he decided to be the first to catch Kira, and to never be Mello's friend again.
And it was the moment he locked his heart.
No one did ever find out that he cried himself to sleep the night they told him Mello had died, and every night since then.