One particular way that you can improve is breaking habits. No matter what level of play you have, there are certain habits in certain situations that you will repeat every single time. Understanding your habits can help improve your gameplay. Also, on top of that answer some questions: Am I spacing well? Am I hitting all of my tech skill (L-cancel, wavelands, wavedashes, OoS options, etc)? Why did he get a kill there? What could I have done different in that edgeguard, neutral game?
Look for your opponents habits. I guarantee you that they have some. Most people use the same recover option or say option to get back on stage from the edge. See how they pressure your shield... do they pressure your shield? These are just some questions to ask after losing a match or during a match. Take time between your stocks.
Overall, make sure your tech skill isn't the problem of your losses because with practice that shouldn't be a reason you should be losing if you dedicate some time each day to it. Hope this helps!
