1. Soften the impact
There's no reason for your break-up to be vicious. Have an adult
conversation and consider the news from your date's
perspective:
Sometimes, little white lies like "Someone important from my past
has come back into my life, and I'd like the opportunity to revisit
that relationship" spare your soon-to-be ex's ego a bit.
Likewise, "I just don't feel comfortable getting involved in a
serious relationship right now" puts the burden of the
relationship's failure on you, in the other person's eyes.
The truth hurts, but it can be couched in sensitive terms. "I just
don't feel it's working between us," may invite some discussion or
even some argument, but it will give you a chance to air your
feelings. Be prepared, though, because it will give your ex a
chance to share feelings too.