for no obvious reason it seems my fitness has vastly improved over the last week.
i just upped my distance to 17k and feel fine. i didn't get the mental and physical barrier i felt after 13k on last weeks 15k. i wasn't trying to push my pace at all, terrain wouldn't have allowed it really anyway, but i guess that helped.
but, i feel basically fine now, like usually after a long run i eat something then get into bed and don't resurface for a few hours but not i feel like i can just go about a normal day.
so fastest 5k ever and longest run ever in 2 days, not bad!