Passed pawn is bad for you in single rook end games. Please help now I found the problem?

Hello everyone,

Only just now the realisation came for me why I lose many single rook end games when I am a pawn up and it is usually a passed pawn as well. 

 Passed pawn is bad for you, I just put that to a get a response to the topic, obviously they are good , but I just realised they can be poisnous for you as well. In a single rook end games, where both sides have a rook I usually end up positions when I am a pawn up and it is usually a passed pawn as well, then I lose.  I  get so excited and push the passed pawn, but later to realise the opposing players can easily defend it. For example in this position, white to move, should be a draw.

1. So what i realised from this is in single rook end games, when you are a pawn up and it is  passed pawn, that doesn't always mean a win. Obviously if the pawn is place really nicely, your king can mop up the other side it is, but in many cases it is not easy as there are pawns on both sides. So I think a very important skill you need to have in single rook end games, in positions like this is to know when a passed pawn is a win and when it is a draw. How can I analyse a positon and make this distinction easily in a rook end game? This is a very important because if you wrongly think your passed pawn will lead to a win and play in a winning style, you will lose the game with your eagerness. So simply my question is their any simple method I can follow to know when to play for the draw or the win with passed pawns. Thanks a lot. 

You can check with the rook the king and push your pawn and king towards promotion so white has advantage.