Where’s your “human spirit, will power and determination”?
I’m not sure why you’re doing doubles now. You need to try to get comfortable covering miles – in single runs.
Someone (I believe Ryan) mentioned Gallowalking. While it’s highly criticized for getting people to run fast, I’ve never heard anyone criticize it for getting people to the finish line. I think every 10-14 days you should be going out for a long walk/run and cover as much distance as possible.
When I was building my long run base a few years ago I’d run 15 minutes and walk a minute. I’d use that minute to take a leak, drink, take a gel, etc. You have to do this right from the start of the run, not wait till “it’s too late.” I think just those little walking breaks can make recovery from your long runs quicker.
I also recommend doing this on race day. Will you look “silly” walking 15 minutes into the race? Maybe. Will you be glad you did 2 hours later? For sure.