Fear of getting things wrong, how to move past it?

[GettingItWrong33]

I'm back to work after 6 years of being a SAHM.
The first month or so went ok, but now when a client complains or I feel that they are unhappy I immediately don't want to do or say anything, because I'm worried I will make it worse or get it wrong.

It happened today, I tried to deal with an issue but I made it worse.

Managers are supportive, but i realty should be able to filter things better.

I feel like I make things worse when I try to solve an issue. Because I'm stupid.

I have a real problem with this. I've always avoided doing things if I don't know how to do them, for fear of doing it wrong.

I'm almost 40 and I feel really really pathetic and stupid.

Firstly, please don't think of yourself as pathetic or stupid, andalso know that youre not alone. I've felt much like this, OP. I felt useless for pretty much all my working life; scared I'd get things wrong at every turn. And anxiety seemed to make mistakes or problems a self-fulfilling prophecy, a certainty. I found it difficult to deliver negative news to customers, or to stand my ground.
Have you asked your manager if there is anything they can do to help, or suggest? Confidence building techniques, assertiveness training etc?

I think I understand. I have a job in events and have had things go wrong through no fault of my own but I've had to deal with the customer fall -out. My advice is to make a flow chart decision tree type thing with exactly how to deal with each scenario. I did this, down to even phrases I could use. I put exactly what to do. I found it reassuring as it means that in moments of high stress I'd have a tool to help me think.
I consulted my colleague on it who is more experienced than me and she suggested some things but also reminded me that I was never (or rarely) alone and there would be other team members I could call on for support.
I have experienced fairly catastrophic event failures (again, out of my control entirely) and was weirdly calm!
I also find checklists checklists checklists really helpful because I know everything is covered and the date when I sorted it. (Also satisfying to tick jobs off!)