You did say "only" marathon WAID, but the gist of your replies indicates you're not done yet? If you decide you are done then take comfort in the fact that you've actually finished a marathon, more than an awful lot of wannabees have managed!
But if not.......
As an example my 1st London was a 4:45 with a "never again" moment at the finish (I was hoping for around the 4 mark), but the nagging sensation that I'd let myself down never went away.
So I trained harder, joined a club, tried and tried again, 1st to break 4, then 3:30 and at last to get under the magic 3 (Failed by 3 min 17 sec, not that I'm bitter)
And now, 30 marathons later, still hoping to get under 4 next week at Halstead, but perseverance can pay off, if you want it enough!
Forgot to add she may be a runner, Rhalou, but as a researcher, writing articles on events she doesn't appear to have run, leaves a lot to be desired.
Doesn't even appear to read RW, as no Halstead, which IS scenic and consistently appears in RW top 10UK marathons and yes, I am biased having run it 5 times, but at least its an opinion based on experience, not organisers puffs.