If something goes to your head, it makes you feel vain. If alcohol goes to your head, it makes you feel drunk quickly.

Examples: Being on Youtube has really gone to his head.[ he's become very arrogant because he thinks he's famous] She should not have drunk the whole bottle of wine. It's gone to her head and she feels dizzy.[ the wine has intoxicated her and affected her ability to stand up]

Two usages: the first is becoming arrogant because of some perceived success. If I win a race and tell everyone, "I'm the best!" then I have let success 'go to my head'. Also, if you get intoxicated from a substance like alcohol very quickly, you can say, "Boy, that drink really went to my head."

If you drink alcohol and you become drunk, the saying goes the drink has gone to your head... Or if you have an idear and it does'nt work, but your still trying to make it work, then people will say 'the idea has gone to your head' hope that helps :D