Be open to any change that may arise physically and mentally and even externally. If we insist that change should take place according to our own idea, then when there is change which does not correspond to that idea it leads to suffering. But by realising that this is the nature of existence, that it changes and that we have no control over change, then if you can be open to change in whatever form it arises, internally or externally, this will result in freedom.
And according to the Buddha, this fact of change and impermanence and this idea of no-self are very well inter-connected, inter-related. He has a very interesting argument. If we own things, if there really is an ego, a self, then we should be able to order things: Now things should happen in this way, according to my ideas. But as there is no self, no ego, we cannot do that. So therefore we have to see from the fact of change, that there is no self-identity, no agent, only the process of change itself.
It is interesting that whenever there is suffering, there is suffering because you want things your way, and this your way or my way is the result of the feeling that you are Somebody. So whenever we are suffering, just find out what is the idea, what is the model that you are holding on to which is now being challenged. It is always some idea of how it should be, how it must be according to the ideas the self has.