Depends on what sense of pride you are referring to. When you say "I'm proud of you" to someone who made the right choice than it's not sinful but, if your defining it as the desire to be more important or attractive than others, failing to acknowledge the good work of others, or excessive love of ones self then yes it can be a sin.
Its a condition of the heart. There is no line exactly, for each person it may not be the same. Some say pride is boasting in yourself or putting yourself above others either with words or with actions. But I've also heard that putting yourself down can also be pride because while you try to put others ahead, you could be putting yourself so low that you focus on your own humbleness and how much you do for others. Self-focus I guess would sum up pride. Yes, it is a sin, but its for each person to examine their own heart to see if a change needs to be made.
Pride is a positive feeling that helps you do better in life. More like a good self esteem. Arrogance is when pride goes too far! Know who you are and celebrate that. Feel good about yourself and respect others. You will be fine.
Pride, as in pride in your accomplishments, pride in your ancestry, pride in any circumstance where it is justified, is not a sin. It's just something you feel. When it turns to arrogance; what I did, what I am, what I own, makes me better than other people -- I hesitate to use the word sin (people jump to such conclusions) but that's where it goes wrong..
In mid evil times St. Thomas Aquinas wrote a book called Suma Theologica (sp?) anyway he invented the idea of 7 deadly sins of which pride was one. His idea of sin was more about character flaws that lead one to sinful actions. Pride, as he explained it, was the sin of forgetting that all your gifts ultimately come from God, therefore, taking credit for accomplishments was to forget that man's duty is to glorify God not himself. Thus: pride is a sin. It's not a modern idea.
I struggled with pride for years, but finally realised it was really my sense of aloneness from god and not believing he was there to help me that was causing my trouble. I believe pride separates us from the love and support of god and this is the true sin.
There is a difference between the kind of pride that God hates (Proverbs 8:13) and the kind of pride we feel about a job well done. The kind of pride that stems from self-righteousness is sin, and God hates it because it is a hindrance to seeking Him. Pride is giving ourselves the credit for something that God has accomplished. Pride is taking the glory that belongs to God alone and keeping it for ourselves. Pride is essentially self-worship. Anything we accomplish in this world would not have been possible were it not for God enabling and sustaining us. "What do you have that you did not receive? And if you did receive it, why do you boast as though you did not?" (1 Corinthians 4:7). That is why we give God the glory-He alone deserves it. Read more: http://www.gotquestions.org/pride-Bible.html#ixzz2NiZVyR5o