Uncertainty about choosing embryo for FET

I’m waiting for my next cycle to begin so we can do our frozen transfer. We have two baby girl 5-day blastocysts that made it through and will choose one with the doctor to implant. This has been the plan since we decided to do IVF this summer but I’m now having some difficult feelings about leaving one of our embryos behind, the daughter we don’t choose. The idea is to put that one on ice for a possible third child (we already have a son), but I’m 6 months away from 40, and realistically, I’m not sure we will be up for doing it all over again in 2-3 years. I’ve entertained the idea of transferring both but am also hesitant about putting all 3 of us at greater risk because of this uncertainty. I just want the best possible outcome and didn’t anticipate feeling this way about the one we don’t transfer. Did anyone else feel conflicted and sad about it? How did you move past it?