Help! I've over cooked my lamb shanks!

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I asked on here for a recipe for the best lamb shanks as it's a birthday dinner in my house tonight.
All was well, I cooked the lamb last night, took it out of the oven, looked and smelled amazing.
I left it out in the casserole dish overnight and had a look this morning - the lamb has dried out and it seems really over cooked and tough, I guess because the stock has reduced too much
I've stuck some more water in a little more wine in the pot and am now re-heating it on the hob to try and tenderise the meat again
Have I f*cked it?
I'm so annoyed with myself!
Should I just got and buy some more lamb and start again?

Too late now, but why cook it in advance?
Left out overnight? Serious health risk.
IMO, re-heated lamb is awful.

It was fine, I re-soaked it in more red wine, and then reduced it down.
No food poisoning, but I've eaten street food while travelling all over the world since being a child with no difficulties - so I have a stomach of iron!