I'm going on vacation instead of visiting my boyfriend
Is this something you have wanted to do?
I have always wanted to travel in my spare time abroad or in another city.
I can understand your reasons for wanting this vacation, however you shouldn't cancel your partner's plans with you. You should let him know what you want to do and see what he thinks. You don't want to ruin your relationship with him.
I need a break from him and I'm doing this for myself.
If you feel that way, then you need to communicate that with you partner. Don't just go on a trip without informing him at least.