Today was a waste of money
No, it wasn't. You learned more than you think.
You learned that simply having flying lessons is not enough; you have to have a plan of campaign and work out how to use your time wisely.
You learned that you are a person, not a machine, and that there will be good and bad days no matter what you do.
You learned to ask for help and advice, and came and posted on here. And do take BackPacker's brilliant advice, which I'm sure all of us will agree with.
You may not have learned yet - but you need to - that getting stressed and beating yourself up because of an apparently bad session is counter-productive; it means you fly even worse and can't learn the things which are there for you to learn within that bad session. You HAVE to relax!
You may not have learned - but need to - that where money is concerned, there's Real Life...and then there's flying. Just don't even think about what it's costing you, or you get even more stressed...and then fly even worse etc etc. You flew, therefore you learned. You will always have bad days, however long you fly.
You may not have learned - but need to - that it's worth analysing an apparently bad session to find out why things went wrong. Was it simply overload - the circuit is tough, and we instructors are sometimes too keen and take people into it too early? Was it stress or fatigue...had you had a tough day at work, a row with a friend? Were you coming down with a cold, but thinking it was nothing; even the slightest thing like that can affect your flying quite dramatically? Or was it just....one of those things, which you need to occasionally accept?
Sounds to me like overall it was a great learning experience and £150 well spent.
