Is it hard for you to express your anger or frustration to God? Do you hesitate to share your pain with Him?
Many of us struggle with letting God hear the cries of our heart. Not sure I understand why, when He already knows full well what those cries are! I believe He wants us to bring Him those cries. It's clearly not a "sin" to get angry and certainly not a "sin" to share that anger with God. He already knows how we feel. We sin when we make poor decisions in our anger...when our choices made in anger become ungodly choices. "In your anger, do not sin." Eph. 4:26
I was angry about being sick and angry that this was happening to me. Ever been there? That anger diminished after I expressed it to God. I can't say I don't have days where I feel it creeping up again, but anger doesn't control my life because I cried out and gave it to God and continue to give it to Him day after day.
Check your heart...are you angry because of your circumstances? Angry because someone broke your heart, angry because you lost your job, angry because your body is failing you? God is just waiting to hear from you.