How Did Alexander The Great's Personality Deteriorate Prior To His Death?

Alexander readily began to believe false accusations that swirled around his court. The preservation of his glory and reputation becoming the most important thing in his life, he administered punishment with the greatest of severity. Having been led to believe that an advisor named Philotas was implicated in an attempt upon his life, Alexander had him executed. Thereafter he sent word to Media and had Parmenio, the father of Philotas, also put to death. This was despite the fact that there was no evidence that Parmenio was involved in seeking Alexander's death.
One of the darkest deeds of Alexander was the murder of his friend Clitus in a fit of drunken rage. Commenting on the incident, Arrian observes:
"[Alexander] showed himself therein the slave of two vices, by neither of which any self-respecting man should be overcome, namely, passion and drunkenness."
However, Alexander came to recognise the baseness of his act. Most ancient historians (according to Arrian) state that Alexander condemned himself for having become the slayer of his friends. For three days he lay in his bed, partaking of neither food nor drink. Finally his friends were able to persuade him to eat.