If you haven't heard Santana, maybe it's time now. This story is brilliant! Plus - there's a historic recording.
In short, he took acid before Woodstock of 1969 because he thought there is a lot of time before going on stage. Just moments after taking the drug, he was told that the only way they are going to play is if they're doing it now.
Here's a link to the full interview:
Peace and love!