The only constant in life is change... sometimes we welcome change... sometimes we dread it. However you take it, changes will happen throughout your life. All you can do is adapt and overcome.
Cry if it makes you feel better, but don't linger in sadness for too long... happier times happen when you finally let go of the sad memories and ideas of what could've been.
"The weakest soul, knowing its own weakness, and believing this truth that strength can only be developed by effort and practice, will, thus believing, at once begin to exert itself, and, adding effort to effort, patience to patience, and strength to strength, will never cease to develop, and will at last grow divinely strong."
- James Allen