Even at the basic cellular level, change is always, and already, happening. Trying to fight it, trying to hold onto things or wanting them to stay exactly the same, is a tremendous cause of stress. Accepting THAT things will change is the key. You don't have to "accept the change" as is - but if you roll with it, you have a much better chance of coming out ok than if you stand stock still and refuse to budge.
It's the flexible branch that bends, the rigid one that snaps.
So much easier said than done - but, then, we don't grow and get stronger when it's easy, do we.