this is my heart's desire

i've been trying to be "obedient" to God's will but i guess i'm still a little confused on the concept. over the years as i've struggled with the idea of "God talking to people" and "knowing God's will", i've had to make several decisions which were torturous. i remember trying to figure out if i was supposed to be a missionary to japan or not, and no option i chose seemed right. it felt like i was making the decisions for the wrong reasons, and i was afraid of not doing God's will. people would tell me, no matter what you choose, God can take any situation and make it work out for the best if you trust Him.

so this is me, following a path i didn't choose, but still trying to trust Him. i don't know what that fully means, because it somewhat feels like i'm trusting in an unknown. i mean, i have faith that He will take care of me, and i have faith that everything will work out for good. but then there are also passages in the Bible that say

"Delight yourself in the LORD, and He shall give you the desires of your heart. Commit your way to the LORD, trust also in Him, and He shall bring it to pass." ~ Psalm 37:4,5

is it possible to still be trusting him if i'm pleading for what i want? or am i supposed to trust in Him and try to change my heart? what does obedient mean? am i supposed to empty out my heart and ask Him to fill it with His desires? the Bible is full of stories of people who have pleaded with God and He's granted them their wishes because of their relationship with Him. but then, some of those stories haven't turned out for the best - almost like it's a "fine, you can have what you want, but you have to live through the pain of it." it's all very confusing to figure out how much i'm supposed to surrender over to God. i've gotten as far as the "trust in Him" and am hoping i can figure out a direction to turn...