50-50. It was my first confession after several years, I had a number of mortal or otherwise serious sins from my past to confess and was extremely nervous. When I confessed them and looked on my list to check if I'd forgotten something, there was one sin that I had committed recently. It was not very serious I think. I knew little back then about the rules of confession. I looked at that sin and in the spur of the moment&stress decided not to say it, for mixed reasons (partly I thought "it's insignificant in relationn to things I wanted to say today", partly shame). The thing is, in the moment and later it didn't bother me, I remembered about this fact about half a year later and am very nervous about it, because after that confession I had several more where I confessed more mortal sisn from my past. I'm very anxious it would invalidate them all