Melee is chess... if you are having trouble, then you don't know enough about the game. Plain and simple as that. You can beat anyone, it just comes down to knowledge. The word 'knowledge' is, however, a very loaded word in the Melee world. Knowledge encompasses every factor in melee (will to win, neutral and punish game, edge guards, perseverance through defeat, constant growth, etc.). There are an endless list of things you can do to improve, so long as you really, really, really want to.
More recently, I felt as though I could never beat my friend. And he's good, so I don't feel bad about the singular loss... but... when losing becomes a constant, and you feel as though there is nothing you can do to beat this person, it can be very difficult to improve. It really started to mess with my mentality, to the point where I probably lost a month of effective training, because I was so focused on beating him. I couldn't stop getting nervous and dropping wins.
Then I started getting another friend of mine into Melee, teaching him everything I know and royally beating the crap out of him... I gained a new outlook for the game, which is what I said before, melee is chess- if you are losing, you don't know enough about the game.
After that week or so of playing my scrub friend, I played my 'good' friend.... and won 7 games in a row right off the bat... I was doing things I would see in videos against him, things i wouldn't normally do, three stocking him over and over. Something inside me clicked, and I no longer felt anything but happiness, whether I won or lost, because I'm playing the game I love most.
Study the gods and everything they do. Play different characters. Look up what you don't know or understand. Keep a clear head. Chew gum. Listen to music. WATCH TAS VIDEOS. Play as many different people as possible. And get gud, scrub (: