“I’m not good enough to pray.”
No, you’re not. Neither am I. Neither is Billy Graham or Mother Teresa. Neither was anyone else throughout all of human history–except Jesus himself–good enough on their own strength and merit to deserve to talk to God.
But God is good enough to talk to us. And that’s what we need to know. He made a way through faith in Christ that we can be in a real relationship with Him. And He cherishes that relationship, because He cherishes us.
God doesn’t hear us because we’re awesome, He hears us because He’s awesome. That means that even I can ask God to do amazing things, and He hears me. Not because I’m great, but because He’s great. And because I took the time to ask.
And since it doesn’t depend on us, we can ask God for big things. (see Eph 3:20 about this). In fact we should ask for big things, far beyond what we could dare to trust for ourselves. Because He’s a big God.
If you’ve failed, take your failures to God. If you’ve sinned (like the rest of us), take your sins to God. That’s the best place you can go. Trying to hide from God or fool God isn’t just impossible, it’s counter to the restoration He is desiring to create in you.