We are tempted to ask God "Why?"
But God says, "How can I give you all of Me, when you're not giving Me all of YOU?"
The more of you that you give God, the more He can act in your life. You need to "fit" Him, and there's only so much space available. In order to make room for one thing (God) you must give up another ("doing you"). Give him every crack and crevice like the pieces of a puzzle: if you start removing pieces that are there, there are spaces left.
We often only make the spaces for God that we want Him to have, but God wants ALL of your pieces - He wants the whole puzzle board. He wants the good stuff, the ministry, the love and forgiveness, but He also wants the hurt and pain, the insecurities (especially the insecurities), the difficult situations, the easy ones, your finances, your choices - for school, career, relationships, even meal choices for some of us!
Don't hold out on God. Give Him all the parts of you - hidden and exposed, and watch those things that you've prayed for Him to handle for you be taken care of, fall off, or flourish (whatever is the appropriate need).
He is God. Trust Him fully and completely. And when you feel your faith wavering, remind yourself (and Him) by saying (out loud), "I trust You, Lord." It's that simple. Romans 10 tells us that faith comes by HEARING... If we want to build our faith to trust God, then hear yourself tell yourself that you do. Only when we fully trust God can we truly give Him our all.
So... you want ALL of God? Then give Him ALL of YOU.
Psalm 139 (the WHOLE thing!)