A noted thinker and writer has said: "Whatever the mind is set upon, or whatever it keeps most in view, that it is bringing to it, and the continual thought or imagining must at last take form and shape in the world of seen and tangible things."
And now, to be as concrete as possible, we have these facts: The body is continually changing in that it is continually throwing out and off, used cells, and continually building new cells to take their places. This process, as well as all the inner functions of the body, is governed and guarded by the subconscious realm of our being. The subconscious can do and does do whatever it is _actually_ directed to do by the conscious, thinking mind. "We must be careful on what we allow our minds to dwell," said Sir John Lubbock, "the soul is dyed by its thoughts."
If we believe ourselves subject to weakness, decay, infirmity, when we should be "whole," the subconscious mind seizes upon the pattern that is sent it and builds cell structure accordingly. This is one great reason why one who is, as we say, chronically thinking and talking of his ailments and symptoms, who is complaining and fearing, is never well.
To see one's self, to believe, and therefore to picture one's self in mind as strong, healthy, active, well, is to furnish a pattern, is to give suggestion and therefore direction to the subconscious so that it will build cell tissue having the stamp and the force of healthy, vital, active life, which in turn means abounding health and strength.
So, likewise, at about the time that "old age" is supposed ordinarily to begin, when it is believed in and looked for by those about us and those who act in accordance with this thought, if we fall into this same mental drift, we furnish the subconscious the pattern that it will inevitably build bodily conditions in accordance with. We will then find the ordinarily understood marks and conditions of old age creeping upon us, and we will become subject to their influences in every department of our being. Whatever is thus pictured in the mind and lived in, the Life Force will produce.
To remain young in mind, in spirit, in feeling, is to remain young in body. Growing old at the period or age at which so many grow old, is to a great extent a matter of habit.