If you are content with how you played, you just have to accept that there's variance in this game, and for every downswing there will be an upswing. Other than that, take the time to learn more about poker, maybe it's not only due to variance but also your skills and/or your game selection. Don't be to hard on yourself, it's only a game after all
Also do you have a significant track record in the games, you are playing? Because if not then maybe you are not seeing a "downswing", but you are just not a winning player in those games. After all its a mathematical fact, that due to rake the majority of players have to lose. Everybody wants to belive, they are among the winners, but that is simply just not the case. And in that case either make a budget and play for fun, try to improve your game or find another game to play. For me personally I gave up Zoom cash games, because I found them very difficult to beat.