Going from a long ride of 25 miles to 50+ is a good jump. It's good to go and really push your limits sometimes and see what you can really do as a max effort. Also keep in mind your body is torched now so take it easy for a couple days to rebuild. Next time think about your pacing over the distance too. I find that if I'm attempting a greater distance than I'm used to I'll cut my pace down for the first 25% or so that way I'll have a decent reserve later. Sometimes it's hard to ride "slow" but usually you'll pass most of the people that took off and left you towards the end I've noticed as they got nothing left.