Always remember Heraclitus: 'The death of earth is the birth of water; the death of water is the birth of air; the death of air is fire, and back again.' Remember too his image of the man who forgets his way home; his saying that men are at odds with their most constant companion, the Reason which governs all things; that their everyday experience takes them by surprise; that we must not act or speak as if asleep, and sleep brings the illusion of speech and action; and that we should not be like children with their parents, simply accepting what we are told.
Life is change. The sooner you realize this, the better off (mentally) you will be.
Found this link, which I think does a good job summarizing Heraclitus' philosophy on change.