I want to call off the engagement. How do I do it without destroying everyone?

The hardest thing to say is often the most necessary. You need to tell your fiancé directly, and soon, that you cannot go through with the marriage. Your fiancé must hear this from you before anyone else in either family. This conversation will be incredibly difficult, but delaying it only amplifies the eventual pain for everyone involved and prolongs the period of uncertainty. When you speak, be clear and direct. Avoid vague phrases like "I'm not sure" or "I need more time." Instead, plainly state, "I have realised this marriage is not right for me, and I cannot marry you." You do not need to offer a lengthy explanation or a list of faults; simply owning your certainty that this path is wrong for you is enough. A soft version, intended to cushion the blow, will only prolong the uncertainty and make it harder for both families to move forward. It feels like you are staring at a chasm, knowing the shock and disappointment this will cause. The printed cards, the family investment, the social standing – these are all real and painful costs. Acknowledge that pain for yourself, but remember that these are 'sunk costs.' They are vastly smaller than the emotional and practical cost of entering a lifelong partnership when you are already certain it is wrong. A broken engagement, however difficult, is almost always less damaging than a broken marriage, especially when children and deeper emotional ties become involved. While difficult now, choosing truth and integrity will serve you, and everyone around you, better in the long run.