Sometimes our minds play tricks on us. When you woke up you had already decided it would be a bad day and then you made it happen. If you had woken up telling yourself its going to be a great day - you might have had it.
I remember when my son was first diagnosed with diabetes - i went online and started reading the mortality statistics for diabetics (not a bright move) - found out that many comas and deaths are at night when their blood sugar drops too low - imagine how well i slept after that? But i was fearing something that so far hasnt happened so what good did it do me. Yes it could happen but worrying about it did me no good and was a waste of my energy. Your bf could relapse but if he hasnt so far then enjoy the day for what it is worth - dont let demons and dark thoughts make you fear things that havent happened - that's a huge joy stealer.