was angry with my boss!

the day before yesterday, my boss looked very, very good when we had meeting and promised me to go for PhD defense next spring.

Yesterday is my last day at school and wanted to say goodbye to him, he changed totally, just asked me for the new experimental results, and looked very mean.

what hell with him? I know that he could not find a good student to take my work, but it is not my fault. he knows I have gotten the offer few monthes ago.