Lust is considered an overwhelming desire in the body brought on by an emotion or feeling. While most notorious in the form of sexual desire, Lust can take on other forms, like a Lust for power or food. The key to this sin is that the feeling drives one to excess, but on how much is too much is up for debate.
The range on what is considered excessive and therefore lustful is pretty wide. On one side of the spectrum we have the desire to have sex at all, or even second glances at a person of the opposite sex as being considered lustful. On the opposite side we have Lust as being considered not a vice at all. So as you can see there's a lot of room for interpretation on this one.
As with all the other sins that deal in excess, this sin can lead to a great deal of trouble. However, the virtue of Chastity can help with that problem. Chastity is simply abstaining from certain behaviors that are considered amoral in by your religion's or society's standards. Again, what that is depends on where you're from and what you practice. For sexual desire this is considered in most cultures as abstaining from sexual practices until marriage, practicing courtly love, and romantic friendship. For the other Lust types it is simply the use of moderation.
This sin is third least on my totem pole of sins mostly because I'm still unsure of what constitutes as Lust in my eyes. My upbringing has been one that I've been exposed to an array of differences on what has been constituted as lustful. By one extreme's standards I am certainly considered lustful, but by the other extreme I'd be considered overly modest. I also do not consider myself too prone to excess when it comes to want of power, food, and other things. So with Lust being foggier than the other four ahead of it, it is listed at number five on my list of deadlies.
Hopefully you all have your own idea of what Lust equates to. If you do, what do you consider to be lustful? Do you feel that this sin is one that you fall prey to? Or are you doing fine regarding this particular sin? Let me know your thoughts in the comments.