"So too the (Holy) Spirit comes to our aid and bears us up in our weakness; for we do not know what prayer to offer...but the Spirit Himself...pleads in our behalf with unspeakable yearnings and groanings too deep for utterance."
(Romans 8:26, Amp)
As long as you live on this earth, you're going to be saddled with a weakness. What is it? The flesh and blood body you live in. It's a body that's subject to death. A body that's subject to the physical world around you.
Your reborn spirit doesn't want to sin. It wants to be completely obedient to God. But the weakness of the flesh causes you to fall prey to the temptations around you.
Does that mean you're doomed to a life of failure till Jesus comes and that flesh body is glorified?
No! It means you need to build your spirit up, to strengthen it, until it dominates your flesh. We are told to crucify the flesh. Your spirit man must dominate your body. Praying in the Spirit by the Holy Spirit applies spirit to flesh. It causes your spirit to rise up and take charge. Just like using barbells strengthens your arms, praying in other tongues strengthens your spirit. You see, your spirit is more powerful than your flesh, and as you give it outflow, the flesh will simply have to yield to it. Most believers don't understand that. They'll be overwhelmed by some sin, and instead of conquering it by the things of God such as praying in the Spirit, they'll simply keep struggling to overcome in natural ways. So they end up failing again and again.
If you're caught in that cycle, take heart! God hasn't commanded you to be more spiritual than you can be. He knows your weakness and He's given you a way to overcome it. He's given you the ability to pray in tongues-- and with your understanding to wield the sword of the Spirit which is the Word of God. And no matter how badly you're failing in everything else, you can do these things!
Be warned though, Satan will try to talk you out of it. He knows that once you learn how to bring the flesh in line, he'll have no foothold left in your life. You'll shut the door on him and he won't be able to get in.
Renew your commitment to praying in the Spirit today. Make a quality decision to follow the command God gives in Jude 20 and "build yourself up on your most holy faith-- make progress, rise like an edifice higher and higher--praying in the Holy Spirit!"