1. Judging others.
Many Christians today feel the need to act as God himself and slander those in sin or those who don't believe in God. They feel the need to publicly point out other's sins without realizing their own. The topic of homosexuality is a great example of this. Regardless if homosexuality is a sin or not, it is not our human right to discriminate against or treat homosexuals any differently than we would anyone else; because we are all in sin. Judging others based on their sins only turns people off to Christianity rather than ministering to them and bringing them into God's house. God loves all of us and looks at all of our sisn the same, so why should we treat anyone any different? In fact, Jesus openly hung out with and ate dinner with the sinners more often than the righteous, because they needed him most.
2. Bad-mouthing the church.
So many articles nowadays are titled "why I left my youth group" or "the reason you shouldn't go to church". Although i agree that some churches and youth groups don't have everything 100% correct all the time, it shouldn't be the reason Christian millennials should stop going. They should instead find a different church, one that is more suitable to their taste. Church attendance is NOT required in order to be a Christian, but is a useful tool in learning more about the interpretations of the Bible, discipline and developing fellowship with other Christians in your area.
3. Understanding the difference between a good and a perfect Christian.
Quite obviously we all realize that none of us are perfect; however, we strive as Christians to be good and pure of intentions. If we were perfect, we would live the exact life of Jesus and never date, or get married, or have kids, or have sex etc. In fact, in Mark, Jesus actually states that divorce is a sin, which is something we easily accept in today's society as a social norm considering how common it is. Jesus lived an entirely different life than ours and it is difficult to depict what Jesus would do in every situation. But this generation needs to get out of the mindset that you should feel ashamed or distant from God, just because you or someone else isn't perfectly in line with everything the Bible says. These differences are meant to draw us closer to God, not push us away.
4. Having a closed mind to other's beliefs or theology.
We as Christians need to have an open mind and consider other's opinions, upbringing, and reasoning behind their beliefs. A lot of people weren't as fortunate as to grow up in a Christian home and have a lot harder of a time discovering their faith, and these things take time. Be patient, and don't feel guilty or upset when other's don't agree with you on everything. There are also some differing views and interpretations of the Bible and what it means to be a Christian, and we should be open to those things as well.
5. Declining Accountability.
It's very easy for us to only pay attention to the grace and mercy aspects of the Bible rather than to feel guilt and shame about our sins; however, we can't forget our guidelines and rules to be held accountable for. I've heard many times "Jesus partied all the time! He told us to drink, and be merry!" This was true, Jesus did attend multiple gatherings and drank wine at them. He did not, however, get drunk and make poor decisions that would fail to glorify God or what Christianity stands for as a whole.
6. Believing that by being a Christian you will have an easier, happier, and more comfortable life once you decide to follow Christ.
This is beyond untrue. In fact, being a Christian and accepting God into your heart can sometimes be the hardest thing someone can do. This gift of Jesus living in your heart comes with a great price and great responsibility (you're practically a superhero now!). The enemy's only goals are to kill your spirit, confuse you, and lead you way from the plan that God has for you. The enemy loves to test, tempt, and destroy us Christians way more than he likes to torment non-believers because when your think about it, he already has them. Satan wants to eliminate the people that take away his followers and glorify God. The closer you are to God and the bigger significance you hold in this world, the more you are going to be tested. There is nothing wrong with this, for it is these trials that allow us to come closer to the Lord every day.