"I could get along so easy and so nice if I didn't have you on my tail" (7).
When George and Lennie show up at the farm,
"Well nex' time you answer when you're spoke to" (26).
After a day's work,
"Curley was balanced and poised. He slashed at Lennie with his left, and then smashed down his nose with a right" (63).
George is expressing his pride by telling Lennie he would be way better off in the world without him. This gets Lennie thinking he should just leave George alone and go his own way. While it may be true that George is better off without Lennie, telling him about it is only hindering their friendship.
Lennie killed Curley's Wife by accident and runs off. Curley finds his wife on the ground,
"I'm gonna get him. I'm going for my shotgun. I'll kill the big son-of-a-bitch myself. I'll shoot 'im in the guts" (96).
When Curley see's George and Lennie for the first time, he doesn't introduce himself and try to be friends with his new fellow workers. Instead being the boss' son that he is, he lets his pride out and gives the impression that he's not friendly and wants nothing to do with them.
"Curley's like a lot of little guys. He hates big guys. He's alla time picking scraps with big guys. Kind of like he's mad at 'em because he ain't a big guy" (26).
During Curley's attack on Lennie, Curley was ignoring the fact that this was his new work partner and continued to let his pride override his actions. Steinbeck is showing the reader that Curley is determined to show everyone that he's the boss around the farm.
After Lennie killed Curley's wife, everybody told Curley it wasn't true murder, there was no intention. Curley, ignoring all of them, went straight to killing Lennie without hesitation, forcing George to kill Lennie himself out of pity. Curley continues to let his pride enforce a bad relationship with his fellow workers. This not only affects George's relationship with Curley but affects how everyone thinks and feels about Curley as well as each other.
Let 'im live!
Curley's pride is ultimately the reason why he picks on people and has a chip on the shoulder towards people larger than him. People hate Curley for the same reason they love Slim - pride. Slim is humble, Curley is prideful and arrogant. Pride can hinder possible and ongoing relationships.