I do whatever I can to laugh it off, because I know that deep down it isn't much of a big deal, even if I'm emotionally invested in it. Don't feel ashamed for feeling sad or upset, you shouldn't be too hard on yourself, it's normal to feel stronger emotions the more we're engaged with something, out of all things in life that supposedly aren't important, our hobbies are certainly the most important. What you need to do is sit back and look at your options, you can try practicing by using save states or codes, either built into this particular video game you're playing, or by things like Game Genie, anything that allows you to practice sections you struggle with the most, so you can get good at it, I know some would call this sort of practice cheating, but I feel that you're just saving time as you can win in those parts you're good at whenever, you don't have anything to prove there, it's just a matter of time. I know it's a lot easier said that done, but try to keep yourself calm and put the controller down if you get stressed out, because from my experience we get worse when we aren't playing calmy, less concentrated. I believe in you, OP!