While many seem to think this is caused by the big size of the diamond or the setting on fine diamond rings, usually a large ring is the culprit.     You should never wear the wrong ring size, because if it is too big, it will slide up and down and around your finger, and if it is small, the fit will be too tight. You may have bought a ring that did not fit snugly even at the outset, or maybe your finger just grew leaner over time. Regardless of the reason, you will be left with a ring that will not sit still as you move around. Resizing This is the best and simplest option to get your ring to fit properly. What you should do is get your finger size measured, and then get your ring adjusted by a jeweler. However, colder weather can pose a problem making the ring looser than it is supposed to be.