Why did George stop being cruel to Lennie?

In Chapter 3, George is telling Slim how he and Lennie travel together. This is odd according to Slim because it is rare. Usually, these types of workers traveled alone, moving from job to job as the opportunities arose. George explains that when Lennie's Aunt Clara died, Lennie just tagged along as George went to work. George admits that he used to play jokes on Lennie simply because he could. But George realized that Lennie...

In Chapter 3, George is telling Slim how he and Lennie travel together. This is odd according to Slim because it is rare. Usually, these types of workers traveled alone, moving from job to job as the opportunities arose. George explains that when Lennie's Aunt Clara died, Lennie just tagged along as George went to work. George admits that he used to play jokes on Lennie simply because he could. But George realized that Lennie would often not even realize a joke had been played on him. Lennie would do anything George would tell him. George even admits to beating Lennie up and Lennie would never retaliate. Then George tells Slim about the time he told Lennie to jump into the Sacramento River to make some other guys laugh. Lennie jumps in and nearly drowns. George pulls him out and thanks George for saving him. George felt so bad that he stopped pulling these kinds of jokes on Lennie. 

"I turns to Lennie and says, ‘Jump in.’ An’ he jumps. Couldn’t swim a stroke. He damn near drowned before we could get him. An’ he was so damn nice to me for pullin’ him out. Clean forgot I told him to jump in. Well, I ain’t done nothing like that no more." 

George adds that Lennie is a nuisance but they have gotten used to each other. George still yells at Lennie but this is the only way he knows to keep Lennie from getting into trouble. The other, mostly unsaid, reason that George is kinder to Lennie than he used to be is the friendship between the two of them. Without Lennie, George might become like most of the other traveling workers they have seen. George notes that there is a tendency for such workers to "get mean." 

"I seen the guys that go around on the ranches alone. That ain’t no good. They don’t have no fun. After a long time they get mean. They get wantin’ to fight all the time."