If you belong to Christ, he will make you more like Him, no matter how hard you try.
If you preach that people need to have more faith, but also teach that people need to work harder to be a good Christian, is that not a lack of faith in Jesus’s ability to change those who belong to Him?
You can’t change yourself to please God. That is the job of the Holy Spirit. All you have to do is stop trying, and let The Holy Spirit work in your life.
We are told by Christian leaders all the time that we need to work hard to find God, that we need earn those crowns with good deeds, we must read the Bible and pray everyday and we must spend time going to church and learning more about God, or we will backslide.
Now all of these things are great and good advise and the logical mind will work on these things in their life. But telling a struggling person, a person who already knows that they are not good enough, and has tried their whole Christian walk to be better, that they are not trying hard enough, will only discourage them, eventually they will just give up. Thankfully God never gives up on us, thankfully when we finally give up and just let God work in us, we get better.
Stop telling people to try harder to be a good Christian. Tell them that the only thing Jesus specifically told us to do is to love each other. Love each other and spend time with Jesus. This is all we are capable of in our current human form. Then have faith that if you belong to Jesus, He will NOT let you go. He WILL work to change you for the better, it may take a lifetime, but He has promised to make us more like Him, no matter how hard we try.