With a dueling app like Duelingbook, you can save and review replays. This wasn’t around when I was a kid and we only played with physical cards.
Reviewing replays of losses and learning from them is a good way to improve at Yugioh or any game. Review it yourself or get a better player to review if you can.
A lot of players call their losses unlucky when they’re tilted when they’re actually making mistakes. In the moment of a match, there are a lot of things we can miss. Maybe a bad circumstance on turn 8 was caused by a mistake you made on turn 3 and you didn’t know it. In hindsight, we can see all the information that was available to us and evaluate our decisions.
Of course, we spot mistakes when they get punished. But we should also evaluate the decision itself regardless of the situation. Sometimes we may get away with a suboptimal play either because the opponent also misplayed and failed to punish it. Or luck. Sometimes the rational play is to play around a card that the opponent is most likely to have; just because they didn’t have it doesn’t necessarily mean you made a good decision overall.
Another tip. See what deck type the enemy is using, and then try to pull up the meta decklist of that deck. Of course, the opponent may be using a different list. But having a pic of the reference decklist live while playing can help you think about what threats you need to play around.