why do I keep losing end games

see the section 'Endgame'...

Improving Your Chess - Resources for Beginners and Beyond.....
https://www.chess.com/blog/RussBell/improving-your-chess-resources-for-beginners-and-beyond
https://www.chess.com/blog/RussBell

You should learn most important principles of a chess game. That will give you a solid understanding of a chess game and you will know what to do in every position. Then, you should optimize your calculation so you don't miss tactics in your games. Your rating will skyrocket. I can help you with all of this. Message me if you are interested.

I've found as a beginner that there's quite different skills involved in openings, middle, and endgames.  I have to learn each separately.

Also, I have to improve my concentration as focus can easily wane over the course of an intense game.  This seems to me to be another advantage in playing long, slow games - it helps develop my focus and endurance.

Post a few examples! Otherwise, we're just shooting our mouths off for nothing

Openings Doesn't Matter 😆

because endgames are the most complicated parts of chess, there are 3 points the starting phase the middle phase and the endgame so use your pieces to outnumber (pawns) the king and if you dont have a rook or queen at the endgame your ducked

I looked at your game against cmorgan07, and there were definitely a few big mistakes in the endgame. While by the time the game reached the endgame you were losing you had opportunities to win and draw the game (of course with correct play). The first thing I saw in the endgame is not endgame specific, and that is tactics, and applying them in the game. Doing puzzles on this site, learning what all the tactics are, and getting better at calculating will improve your endgames as well all other parts of your game. Also you are moving way to fast which is a big reason why you are missing ways to get back in the game, and convert on winning chances your opponent offers. 

I would say you reached the endgame at move 29 right after you won the queen for a rook with a rook fork. You immediately go for trying to gobble up pawns with your rook (which in many situations is the best thing to do, but not in this situation). You are down an entire bishop, and your only positional advantage you have over your opponent is that your rook is active, and his bishop and rook are on the back rank.  The key to making this position as hard as you can on your opponent is to keep the bishop pinned to the rook making it hard for them to activate their bishop, and rook. So your move of Rxd5 on move 33 is a mistake. You give up the pin on the bishop which allows your opponent to activate their rook and bishop. You should have got your king off the back rank. You did do that the next move, but your opponent did not activate their bishop to prevent you from pinning it. Your move of Kg2 was a mistake because you could have pinned the bishop to the rook again, but didn't. Kg2 is what you should have played instead of Rxd5 the move before. You had a good idea by trying to activate the king (which is an endgame principle so good on trying to do that), but the pin is way more valuable. Also now you have a past pawn on d5 which can black can stop, but not without making their king move away from helping their pawns on the king side which they need (you were still losing at this point with correct play  on both sides, but you would have forced black to have to play correctly vs if they had activated their bishop, then they don't have to play so accurately to win the game). 

Make sure to take time before you move. You had tunnel vision on checking the king. You had over 7 min left on the clock, and missed the pin with your rook on move 39. You played Rh5+. You should have played Rd6+, and that forks the king and bishop. This would have won the bishop for nothing, and would have evened up material for you. This would have given you winning chances (although for someone at your rating would have been difficult to convert). The reasoning behind that is that you have even material in the endgame, and your pieces are way more active vs your opponent whose rook is on its starting square. On move 47 good job on seeing that they left their rook hanging. This evened up the game.

Don't make a move just to make a threat. That is what it looked like you did to me on move 53 (which is a blunder). Your opponent did not play the difficult position from move 47 correctly, and allowed you to get a winning advantage. You played Rf2 which allows them to protect both pawns with the bishop, and now all black has to do is move his king around and it is a draw. Correct move is to play Kxa5. This would have created a passed pawn that with correct play is a win for you (although you would need to know some about king and pawn endgames and opposition to win it, or how to checkmate with king and rook vs king depending on which line your opponent plays). Correct line is 53. Kxa5 Kc3 54. Ka4 Kd4 (black at this point can choose a line that would trade the trade the pawn for the bishop later on to stop it from queening if they want to, but I will show the other line here) 55. Rxa3 Bxa3 56.Kxa3 Kc5 57. Ka4. At this point you would need to know opposition to win as black could try to get creative, but if you know what to do then they are toast. 

You should focus on 1. Taking your time to think through your moves, and look at the entire board before moving 2. Study tactics which for anyone at your rating is the most important thing to study. 3. Learn the overkill mates (King and Queen vs King, King and rook vs king, two queens vs king, two rooks vs king, queen and rook vs king), and be able to do them in 30 sec or less in a game. That way you can do it in time pressure. 4. study the principles of the endgame more. 

Hope this helps. 

Here are some thinks that will be helpful: 

https://www.chess.com/article/view/chess-tactics (you only need to focus on pins, forks/ double attacks, skewers, discovered attacks as these are the basic ones, and more advanced tactics are typically built on these tactics)

https://www.chess.com/article/view/chess-endgames (principles of the endgame article) https://www.chess.com/article/view/inch-by-inch-row-by-row

https://www.chess.com/article/view/basic-checkmates-the-queen-dance

https://www.chess.com/article/view/basic-checkmates-king-and-rook-mate

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