Hiya Bud. Just to add a couple of things --

-- As well as attributing things to fatigue (right on), emotions are especially energy-demanding in themselves, = mega-tiring;

+ It can be VERY hard to be properly aware of how tired one is, after TBI-ing. You may think you know when you're wiped out, and know that it's sooner/faster than you were used to, but the chances are you may be closer to a wipe-out threshold some of the rest of the time (... but family / people close to you may learn to recognise signs of getting tired before you do).

-- In my opinion, touch (from/with a loved one) is potentially mega-wonderful maybe partly because it's like direct emoto-cution (to invent a new ugly word, sorry!) in that it's so ultra-direct and circumvents all tangly cognitive processing for something like emotional electrocution, but being a good kind of electrocution, if you see what I mean.
... as you probably know now, Mark's "lability" more or less means rollercoasting on emotions.

-- To be uncheerful, a really big problem arises for lots of us, I think, that sleep's not sufficiently energy-restoring. There's a long-long-long-standing difficulty that it's difficult to get re-charged enough (to prolong the tricky electricity metaphor). However, a bit more cheerily, I think that gets better for many or most of us. ... Individually, for my own part, I used to get absolutely floored so often, without warning it seemed, completely like a thunderbolt hitting out of the blue, so that I just HAD TO lie down and close my eyes (practically anywhere!) ... like a total system-"close-down", but that's improved a huge amount. Me apart, I think that managing energy and not being so consumed by fatigue seems to improve for lots of people I've met, altho it takes variable lengths of time and/or is difficult to monitor.

Mind yourself well.