TRANSFER THE PAIN - this is one of the best way to survive, this is one of the best way to alter your situation, emotion and expectation. It's all about finding what pain hurts you the most and transferring it to another place that will make you feel better.
If your knees are aching for whatever reason and it is disturbing your training, it is making your confidence go down so you can't practice very well, it is making you unable to move like you use to move before because you are thinking of getting hurt even more. What you need to do is transfer the pain of your knees to the other parts of your body. Make some of your body parts that are not injured sore. For example, make your abs sore by sitting ups for a lot of times. Or you can also make your biceps sore by lifting heavy weights. The pain on your knees will be diverted to the other parts of your body that are sore and you will be able to forget the injury on your knees. Not only you will forget the pain on your knees, the other parts of your body will also become stronger, you will gain double benefits.
If you are experiencing a lot of mental pain because you are experiencing some problems such as financial problem or love life problem, you can also transfer that mental pain to other things. Work hard, divert your mental pain to work so you will forget your problem, it is a win win situation for you. You will be able to do a lot of work and finish a lot of things and at the same time you will forget your problem easier.
Pain is very easy to neutralize or even remove in your system. All you have to do is choice a pain that has more benefits and focus on it. Your situation will be better and you will slowly be able to change the results in your life.