Trust requires relationship
How long does it take you to trust someone? This question probably doesn't have a generic and quantifiable answer because it really depends on the person. For some people it can take longer, for others shorter.
But there is one key element in developing trust...and that is relationship. Realistically speaking you can't really build trust if you haven't taken the time to build a relationship. It's hard to trust someone that you don't know well or haven't spent enough time with to know the kind of person they are, their character, morals and values.
It can take time and investment on both ends, but that is how you grow to trust someone. And it's not enough to simply know about the person. Many times we can know the whole biography of another person but still struggle to trust them. Why? Because we didn't take the time to actually KNOW them and build that relationship.
So let's apply this to our spiritual life. Trusting God. Man does that term ever make many of us squirm with hesitation, but still hold that desire that we want to trust Him. So why is it so hard?
I feel the answer is just as simple as with any other person...we haven't taken the time to truly build on our relationship with God. We maybe know a lot about Him, but haven't actually spent that quality time with Him to KNOW Him. It's hard to trust someone that we haven't taken the time to know, and we hesitate to trust because of that.
The stronger our relationship is with another person, our hesitation to trust them drops down to barely any. The same is with God. The more we dedicate our time to grow in relation with Him and get to know Him, the more our hesitation to trust will disappear. So when those difficult moments come and our trust becomes tested, we won't be as hesitant or afraid because we will KNOW God on a deeper level, because we took the time to build that relationship with Him.