I'm sorry to hear that you are feeling so frustrated with what should be a pleasure for you. If we are all honest, though, I think just about everyone has felt this way at some point or another in their quilting journey.
It sounds as if you are your own worst critic - which is also quite common. Not sure I have any concrete advice I can give you, other than to put things aside for a bit, maybe flip through some magazines or inspiring blog posts, and give it another try when you feel less stressed about it. Don't feel you have to rush, allow yourself the time to enjoy the process. Cut slowly and carefully, and piece the same way. Savour the steps rather than rushing. If you feel yourself getting tense, set it aside.
With two machines plus a long arm, you've surely invested a lot in this hobby. Are you feeling like you should be able to create fabulous pieces as you have the right toys? I have to remind myself that everything takes practice, regardless of the equipment. I don't think I'll ever have a LA - no room, and don't want to invest that much in it. For me, sending my tops out to other folks is a better choice.
If you have project that you really, really aren't liking, give yourself permission to repurpose the supplies, or pass it on to somebody else who might like it. For me, that meant that the OBW that I wanted to try was never more than triangle strips lined up together. I'd tried the process and didn't care for it. I'll put a garbage bag over me so all of the OBW lovers can throw tomatoes - but I really just don't like them. I don't know why, I love stack and whacks and 4-patch posies, which are along the same lines.
If you can, I'd try to find somebody you can work with, hopefully in person, but if that won't work, hook up via e-mail, etc. Maybe you'll only be able to get together one afternoon a month, or even less, but you will enjoy the time and learn from each other. Is there a fabric store that you might be able to put up a post in, or pennysaver? Or, put up a thread here. I'm constantly amazed how many people mention, "Hey, I'm only an hour from you," or something like that.
Hope you are able to find a way to enjoy quilting again.