Because...

Barcelona, Spain - Circa 2014

Because sometimes, all you need is a photo, to remind you that you had been happy most of your life. Memory of happiness may fade away but having something to remind you of your happiness will sometimes help you go through whatever loneliness, unhappiness, soul searching-need-feeling you're into. 

That you had been happy and you can again be happy. That you have a purpose in life and you need to continually push yourself to achieve that purpose. That God has been and still is good to you. His grace is sufficient and His love everlasting.
It's hard to appreciate life when you're at the bottom, when you just want to give up just to get it over with. Then you become happy again, love your life again... and would want to stay that way for as long as you can.
So, pray.. that God would remind you of those happy memories and for His comfort, love and grace to keep you in such times when you feel that everything is about to burst. Walk down the memory lane with God and know that everything's gonna be alright.
Remember, this too shall pass