Breaking up is never an easy thing to do, especially around the half-year milestone, when partners really begin to feel comfortable with and trust one another. If you know the relationship has reached its end despite the fact that your boyfriend is a really nice guy, the best thing you can do for him and yourself is to end the relationship clearly, directly and respectfully.
Think things through before you act. Make sure that breaking up is really what you want. It isn't fair to put your boyfriend through the highs and lows of breaking up, making up, and breaking up again. Also, if you change your mind, your ex might no longer be interested or available.
Think about how your boyfriend might react, so you can prepare to deliver the news in a sensitive way. If he's likely to get very upset, it might be best to go over to his house where he doesn't have to worry about other people seeing him cry, or so that he won't have to drive or walk home while upset. If you think he might become angry, a neutral, public place is best.
End the relationship in person. Don't avoid your boyfriend or break up with him over the phone or through a text message or email. Do it face to face, out of respect for him and the time the two of you shared.
Be direct and honest. Acknowledge the good times you shared or a quality that you genuinely like about him, but then move on to your reasons why the relationship isn't working out for you.
State that you want to break up in clear, simple terms. Anything less can send mixed messages about what your intentions are. He needs to know that this is the end of the relationship, so that he can begin to move on.
Be sensitive to his feelings. Say you're sorry that this hurts, but reiterate that ending the relationship is what's right for you.
Give your boyfriend the opportunity to talk and express his feelings. Listen to what he has to say, and say something kind or positive in return -- just don't say anything that could lead him to think there's a chance that the two of you will get back together in the future.
Give him time and space to heal, but follow up with a friendly message so that he knows you still care.