36:19 sounds quite brutal for the Peaks. I was happy twiddling along on 32:16 until I moved to Dartmoor and now use 32:18 which seems about right for most of the riding I do locally. I do now also have a geared bike which I used for longer and tougher rides but it probably still works out 60/40 in favour of the singlespeed.
For the sake of a cost of new rear sprocket you could try gearing down a bit – try a 19 or 20 on the back, and if it doesn’t work out then just go back to your gears.
Not worth beating yourself up about either way – the whole point of singlespeeding is that it should be fun, so if it’s no longer so then don’t do it.
If you go back to gears you can always build up a cheap singlespeed from the parts bin / classifieds should you want to give it a go again.