I have a concentration coach, but I always seem to forget the lessons.
Do chess psychology coaches exist? Where do I find one?

Try practising mindfulness meditation. Have a look at Kabat Zinn, he has got academic credentials. So does Russ Harris. good luck.
My problem is more overconcentration ; I put so much effort into the first 50 moves that I have no energy left.

cation? what is that?
Ok so I really don't know what to say. Your rating is higher than mine, so I don't have anything really useful to say.
(But that has never stopped anyone here before)
So, I don't know what time controls you are playing and your opening repertoire. But if you just limit yourself to a few, and take time to study them, going over it slowly and not straining yourself, so that you know what is going on in each critical position, then when you play games you won't have to strain so much to find good moves.
You should know what moves are the winning lines and which ones losing for both sides. That way you are not killing yourself for at least, say the first 20 moves.
Ok that is a hight number, but with enough home preparation, you'll save energy for the middle game. So you'll be full tank for the rest of your 30 moves.

if your mind is wandering you're probably better off focussing on the things that your mind is wandering to.
I was adding cation to the previous post that someone did of California = californication
Um. Billyblatt, that's a good suggestion. But my opening repertoire is what they call a rubber band repertoire - that is KIA, Reti, Larsen opening etc where there are no real "lines". You shuffle pieces around. Hopefully towards a positional end, of course. But it's not like say the Dragon
The game in question was not on this chess site. I don't want to post it. Suffice to say that I was winning for 50 moves and then lost concentration with a horrid blunder that gave me a dead lost endgame that I lost at move 70.
Put it this way. Concentration is a bigger barrier than technique for me to get to 2200ish OTB. I woul;d say that I am 1800ish because I need 100 pts of technique and 300 pts of concentration.
I overconcentrate. That's what I do. I work TOO hard at the board. Most people don't work hard enough. But I work too hard. I need to work less. I will be the world's first LCM [ lazy chess master]
if your mind is wandering you're probably better off focussing on the things that your mind is wandering to.
Yes. It willwander to a long and winding road.
Imagine saying to Dr Phil "I have a rubber band opening repertoire".
Dr Phil "in the 30 years that I have been doing this job I've never found anyone describe a sexual aid and chess in a sentence".

cation? what is that?
A cation is a positively charged ion, although I'm not sure how it relates to the topic...

cation? what is that?
A cation is a positively charged ion, although I'm not sure how it relates to the topic...
Are there any chess coaches in the world who specialise in the areas of chess pscyhology and chess concentration? In particular what to do if you are aware that your mind is wandering.