Learning to Let Go
I can tell you from personal experience that letting go is honestly one of the most difficult things we have to deal with. Most people think of letting go referring to a relationship, but letting go of a life long dream, letting go of a family member or friend, or even letting go of a certain perspective you personally deal with are all difficult and disappointing to experience, but through God's grace you can take a miserable experience and turn it into a blessing.
The best and hardest advice I can give you is to trust God's plan. I know how hard that is sometimes especially when we have to give up something we truly wanted but God only puts things in our lives for His purpose and He takes them away when they detract from His plans. When it's hard to let go of things that I desperately wanted I remind myself that I do not know what is ahead in my future, my plans are nowhere near concrete BUT God does, He knows every bit of my future. Every mistake I will make, every let down I will experience, every joy, and heartbreak. Why would I try to control my future when I can't even see what's gonna happen tomorrow, but God knows it all.
"Trust in the Lord with all your heart; do not depend on your own understanding. Seek his will in all you do, and he will show you which path to take" - Proverbs 3:5-6
Realize that this one event will not dictate your life as long as you think it will. If you do not get that job or that particular guy, your world will not go crashing down, it will be ok with time. Pray for guidance and confidence and that God would be with you to hold your hand through this difficult time.
Letting go isn't about losing something, it could be about gaining something; self-confidence, strength, self-approval, but most importantly a stronger, deeper relationship with Jesus. Our God is amazing, perfect, and loving, but he is also a very jealous God. He wants to be the center of your life and if you place something earthly in His place He will remove it. He has so much better waiting for you, I promise, you just have to be like Peter Pan and have faith and trust.
Have a grieving period, there is nothing wrong with disappointment or sadness. One of the most therapeutic things to do is honestly to let yourself binge on ice cream and a good cry. DO NOT DO THIS FOR TOO LONG, keep in mind it's called a period not a lifetime. You will get back on your feet and succeed but sometimes you need to let your emotions out and take care of yourself.
Honestly, I'm not an expert at letting go and it's something I'm currently dealing with now but if it were easy we wouldn't need advice on it! Always remember that you are God's chosen creation and He loves you above all things. He wants nothing but the best for you like any good father does. Sometimes that isn't what we want but everything will work out in HIS perfect timing. Trust Him in all things, pray even when you've already prayed about it, love yourself as God loves you, and never be afraid to be excited for what's to come."For I know the plans I have for you,” says the Lord. “They are plans for good and not for disaster, to give you a future and a hope." - Jeremiah 29:11