Everything changes, its the fundamental law of the universe. When we look at the mirror everyday, we grow attached to what we perceive to be "us", our bodies and our personalities. However, we all know that we change every second from the moment of our conception. The sooner you embrace the changes, the easier it is for you to accept that life is impermanent. Suffering is impermanent, happiness is impermanent, every emotional and mental stage is impermanent. Peace will flow once this is truly embraced by you.
We sometimes do funny things, like living in the past or in the future. We rehash old conversations and scenarios over and over again. We dwell on what could've or should've been. We day dream about what life could be once we are retired. This isn't reality. Life happens now in the present moment. If you are experiencing pain at this moment, be with the pain. If you are experiencing joy at this moment, be with the joy. Be with what you are 100% at any given moment. Be present and experience what it is happening now.