In the autumn I'm gonna go and wild camp solo for 2 or 3 days, probably in the Brecon Beacons; I want to use the time to practice and teach myself some outdoors skills - what do you suggest?

I've got some outdoors skills from army training, but not really any proper bushcraft stuff - what are skills I could teach myself with a few days outdoors alone? Definitely firelighting and practice navigation (including night nav), but what else? Also, any generally fun activities to do when solo camping?