As Maitriyogi said, "Oh King, this body, which is like something you have borrowed for a short time and must return, while it is still free of illness, not excessively feeble or old, it should be used well." - to achieve something truly useful for ourselves and others - "to overcome the fear of illness, ageing and death." While you are still in good shape, you must use our present life to put yourself in a position where you no longer need fear illness, ageing and death. Failing this, "once you are in the grip of illness and old age..." -once you have become very old and decrepit or have contracted a mortal illness - "....although you may wish to achieve these goals, you will be incapable of doing so." - even though you decide to work for the sake of yourself and others, it will be too late.
These few worlds "this body, which is like something you have borrowed" are indeed significant. You do not control a borrowed object like you do something you truly own: one day you must return it to its owner. The body you call 'yours' is similar in that one day you have to "return it", to give it up. Each of you has a borrowed body. some of us will not have to return it for some time, some will have to give it back in ten or fifteen years, others in to three years, and others yet sooner. it is impossible to know. You have the impression, however, that your body is yours and yours forever. This is true of your body, it is also true of your house: you think of it as yours forever. Ultimately, what can you call "home"? Where is "home"? There is no place where you can stay forever. Although this is the way things are, you see them differently. We only decided it was ours. Where is the body that is really ours? Right now you only have one body, and the one you have was formed from parts of our parents' bodies. So it would seem thee is no such thing as a body you can truly call your own.
Dagpo Lama Rinpoche Jampa Gyatso