How to Break Up with Someone
Breaking up is rarely easy. You both had feelings for each other at one point, and maybe you still do. The key is to do it maturely, without deliberate pain, so that you can both move on with your lives and find someone better suited for you. A relationship really needs two fully committed people, so if one of you doesn't want to be in the relationship any more, it's best for BOTH of you to end it. That's the key message to get across.
Don't get into lots of blame-finding. There is always fault on both sides in a relationship that fails. Make sure you sit down face to face somewhere quiet. Never break up over the phone or via email, that's completely unfair. A relationship is based on trust and dependability - don't prove you're unworthy of that in the final hour. Sit down and explain it's not going to work. If your partner has questions, answer them as fairly as you can, but without going into lots of back-stabbing. Breaking up isn't about finding fault. It's about you both being able to find "closure" to this relationship so you are able to then move on to a new one.
It's really in both of your best interests to end this cleanly. If you don't, it will come back to haunt you in many ways. If you can both accept that this was simply not meant to be, and that somewhere out there a new person awaits which IS perfect for each of you, you might even be able to stay friends. Or if not, you can look back on your time together as an enjoyable experiment which just didn't work out the way you'd originally hoped.
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