I'm going to break up with my boyfriend on his birthday.
Why would you do that? Is he aware of your intentions?
Yes, he will feel less sad knowing the reason why I broke up with him.
That's a bit rough on your part for choosing his birthday as the day. It's your choice, though, so do what you will.
You're not telling me how to live my life.
What I am telling you is that it is extremely cruel to leave someone on their birthday. You really should do it before his birthday at this point if you're not feeling love for him anymore.