George feels responsible for Lennie. He made a promise to Lennie's aunt which forces George to care for Lennie. George tends to lose his patience with Lennie since he’s mentally disabled he tends to do things that are quite stupid and not human like. Lennie sometimes thinks it’s best to run away so george doesn’t feel so burreden with the price of taking care of him all the time. But deep down inside George knows he can’t live without Lennie, being mentally ill or not.
Lennie's disability keeps people from treating him normally. In Of Mice and Men, when George and Lennie are in the barn, the workers can't help but notice that Lennie is different. They think no good of him which makes George angry because he thinks that they will sabotage their work and make the boss fire them.
George is a short guy but likes to get the job well done, Lennie is a whole different case. Lennie is tall and mentally Ill, worst part is that he’s a grown adult that still needs to be told what to do. Lennie’s disability keeps George from achieving his goals which makes him angry all the time.