8 - Christians always tend towards legalism or antinomianism.
Our Lord refers to His way as the narrow path. A path that is narrow is easy to get off of. There are two major ways in which Christians step off of our Lord's path. These are legalism and antinomianism.
The first danger is legalism. This we see quite clearly in Scripture, from the Pharisees to the Judiazers and the like. What happens is that the Law ends up replacing the Gospel as the Christian's love. Rather than with joy clinging to the Gospel, our view of the Law can become warped, and we forget the second use - we forget that the Law shows us our sin. When this happens, we slide to legalism. We substitute rules for freedom - we start mandating that the way in which we happen to use our freedom is the best way and that to be a good Christian you need to do X, Y, and Z - where X, Y, and Z may be not drinking, may be making sure you chant, or may even be simply "knowing" that you are a better person than your neighbor. We abuse the Law, and fall into legalism. Legalism is a rejection of the Gospel, substituting self-righteousness for the righteousness of Christ.
The other danger is antinomianism. This is a desire to do away with anything to do with the Law (one might say it is the extreme opposite reaction to legalism) - and the desire is to assert your freedom over and above any and all conventions and rules. With this, people either become incredibly independent (I can do what I want) or incredibly indifferent (what does it matter, we all go to the same place, after all). The thing that antinomianists forget is that to reject the Law and be opposed to the Law is to be opposed to love. The Law is love - and to reject the Law and treat it as unimportant is to reject Love - and hence also the God who is Love and Who makes us to be like Himself - one who loves. Independence destroys love - for it denies that we are beholden to one another. Indifference destroys love because it does not do.
Christians tend to fall to one side or another - legalism or antinominianism (which I know I am mispelling, I think - bind me by your random laws of spelling, will you Webster? I think not!) for one simple reason. We mistakenly react to a wrong view in the wrong way. We see a legalist, and we reject the self-righteous nature - and we are determined to demonstrate our freedom -- and yet we forget to do so in love. Or we see people using their freedom in ways that probably aren't that wise - and so we make more and more rules to be safe, and we shake the finger and wag our tongues - and we fall to self-righteousness ourselves.
The proper solution to both of these issues is not over reaction (which we sinful humans tend to love) but proper Law and Gospel preaching. As in all things where there is a human fault - yes, demonstrate the Law - say you are not fulfilling your duties, say you are overstepping your bounds -- but then the move must be onto the Gospel. Both these two are the common ways of falling off our Lord's path because they forget that He is the Way we are to be on - and they both slide away from the Gospel that Christ Jesus is our righteousness.
Hence, why we must always pray, "Lord, I believe, help my unbelief."