When we watch beginners play games. Most games end up in checkmate in middle games. But still some end up as one side has a queen or two rooks and another side has a lonely king, the winning side can't make the kill. They move round and round, but have to shake hands in the end. It's very sad to see such a scene.
Not only beginners have difficulty with endgames, but also masters sometimes do. We had the famous game that a WGM could not find a checkmate in NB endgame.
Improving your endgames will greatly improve your winning rate. At 2000 level, at least half of the games end up in endgames. If you could win half of them, your winning rate will at least double.
In this summer, I will teach "Introduction to Endgame" course online. Details can be found at http://www.chessstepsonlinelessons.com/