What did Albert feel the medical certificate "Allmost burning a hole in his pocket" ?

Albert Einstein was under the notion that the medical certificate would help him take a break, for about six months, from school. However, when he did go to school the following day, he was informed by his teacher, that he was being expelled from school. This terrified Albert and at that moment the certificate in his pocket seemed to remind him of the ruse he was going to play. The entire situation made Albert sad and confounded.