Well, it's something unclean/disobient/against God's Word, what He wants us all to do, but it's also something that we all are gonna do anyway, but can sin less with His help. Just confess sins, & mean it, then it'll be ok. =)

Not on purpose, but to me sin is human nature..sometimes..

to me, sin is giving the devil a foothold, giving into wicked temptations and deeds, and delibrately ignoring the word of god. sin is listening to your own selfcentred desires, and doing as YOU please. not what god wants you to do.

But, yes, unfortunately it is human nature. But I also understand that if there was no sin, we would never mess up, and learn from our mistakes.

Sin is human nature and most of the time we don't even know we do it. Here are some examples of Biblical sins:

Get an abortion (Yes, Christians are the number-one customers!)
Not abstain from the appearance of evil (Christians don’t like Goodfellas or the Sopranos?)
Accuse others (Christians are always accusing others, just look at the right wing)
Not acknowledge iniquity (By being anti-gay, they’re breaking this!)
Commit adultery (50% of all marriages ending in divorce says somebody’s cheatin’)
Look at a woman with lust (Umm, beer ads? Sports Illustrated Swimsuit? Hello!)
Be afraid of people (So, Christians don’t fear robbers or rapists?)
Have unjustified anger (Nobody’s ever been in a bad mood, huh?)
Be angry with your brother (Yeah, brothers never fight!)
Be anxious (Well, explain the shrinks and billion-dollar Xanax industry)
Argue (Seriously? Arguing is a sin against God! Name the person who doesn’t sin)
Arrogance (Hey, just believing your religion is the right one is arrogant)
Be ashamed (We’re getting into “LOL” territory here, but anyway…)
Commit assault (It’s not just atheists filling those court dockets!)
Believe astrology (Again, it’s not atheists buying those horoscopes)
Babble vainly (Any cocksure “I’m the best” stuff qualifies)
Back-bite (Ever speak behind someone’s back? Sinner!)
Baptized before accepting Jesus (Every baptized baby ever…sinners all!)
Bitterness (Yes, if you’re upset over something, you have sinned against God)
Not bless those who curse you (If you get a FU from someone, you sin unless you say thanks)
Not bless persecutors (If you get falsely accused of something, again, you must say thanks)
Eat blood (Do you like rare steaks? Well, the bad news is you’re going to hell)
Boasting (Oh, you want to show off your collection? Try it in hell, buddy!)
Judge (If you form opinions about someone, good or bad, you have sinned)
Not feed the hungry (If you don’t voluntarily feed the hungry, you are sinning)
Not shelter the homeless (If you don’t invite homeless into your home, you are sinning)
Not visiting prisoners (If you don’t visit inmates, you are sinning)
Not receive sick children (If you don’t take in sick children, you are sinning)
Touch! (That’s right, Scooter. If you even so much as touch God’s servants, you have sinned)
Be a busybody (Not really sure what this means, but if you’re active, you’re a sinner)
Be carnal (You like to be horny and have good sex? See how you like hell, mister!)
Not have charity (If you’re not giving to charity, you’re a sinner)
Not spank a disobedient child (You read that right; you are supposed to beat unruly children, and to not do so is a sin against God!)

By the way this was not written by me. It's from another website. Mighty entertaining though.

the only poeple who have a right to judge god, are those that have never sinned.