An essential part of Christian living involves obeying -- or at least making the attempt to obey -- God's commandments. Part of the difficulty of this may lie in our distorted thinking about the nature of God's commands. It is important, therefore, think rightly about them so that we may help ourselves on our way.
To this effect I want to quote a line from St Anthony the Great:
Just as sailors guide a ship with care, so that they don't strike it against seen or unseen rocks, in the same way those who strive for a spiritual life ought carefully to search into what they ought to do, and what they ought not to do. Likewise they ought to believe that God's laws are useful for them, cutting all sinful thoughts from the soul (On the Character of Men and the Virtuous Life, 16).
Living a spiritual life, as Anthony insists, is like sailing a ship. You are your own ship, and you have to know where to go and where not to go, what to do and what not to do. Otherwise you may find you are leading yourself into a life of sin and spiritual death, rather than the spiritual life you set out to pursue from the beginning. But for this you need guidance, and this guidance has been given to us in God's commandments. Consequently we must think that God's commandments are useful and good; we must be ready to hear them and take them as sage advice, directions so that we may arrive at our destination.
If we love sin and are happy living a life as we see fit, then God's commandments will seem a burden and an obstacle to a life well lived. But this is all the same with not believing God, who insists that Happy are those whose delight is in the law of the LORD, and on his law they meditate day and night (Ps 1.2). God tells you that it is not right to live in the things he calls sin, and that in fact they will lead away from your happiness. Rather, true happiness comes from a life lived in accordance with his laws! Obedience to the laws inspires others to say: Surely this great nation is a wise and discerning people! (Deut 4.6).
If we are to believe God, then we must take his word about what is right and wrong, good and bad, healthy and unhealthy. We can't presume that we know better than him, but must be willing to receive the commandment he gives us as one who knows better. If we're going to live a true spiritual life in fellowship with God, we have to trust him that the commandments he gives us are useful for us, as Anthony says, and are worth obeying.
Even obedience, then, is subsequent to faith. If we are to obey, we first have to trust God when he tells us that it is better to do things his way than the way we think is right.