"For I say, through the grace given unto me, to every man that is among you, not to think of himself more highly than he ought to think; but to think soberly, according as God hath dealt to every man the measure of faith." (Romans 12:3)
Paul says here that we should keep things in perspective when we introspect. He states the same, however inversely when he says "in lowliness of mind let each esteem other better than themselves." (Philippians 2:3) It takes time but learning to see ourselves as God does is worth the effort expended.
Watching from the fence
"Verily, verily I say unto you, He that entereth not by the door into the sheepfold, but climbeth up some other way, the same is a thief and a robber." (John 10:1)
A state of indifference and indecision as applied to ourselves is not possible. We live our lives, day in and day out and a thousand micro decisions make up our internal view. And in the heading verse, Paul doesn't say not to think highly of oneself. Just that it be tempered with and by reality. This is why it's important to have friends who see the real you. They won't let you stray into a gray area where you're just not quite yourself. Think soberly. A...designated driver, as it were, for your person.
The above verse applies to the church and the Body of Christ. But a narrower interpretation could be seen as applying to us as an individual. As Jesus is both God and man, He was able to live everyone's life. In His. Vicariously. So He knows you better than anyone ever could. Even your closest friends, those whom He speaks through with frequency and who "get" you, don't know you like He. Even I don't know myself better than does He. And if you give Him the key to your gate (better yet, make Him your "door") He'll ensure no one gets in who doesn't belong.
"And I find more bitter than death the woman, whose heart is snares and nets, and her hands as bands: whoso pleaseth God shall escape from her; but the sinner shall be taken by her." (Ecclesiastes7:26) Just because it says "woman" doesn't mean a "man" won't act the same. I find that when someone doesn't know how to see themselves in light of God--the God who truly sees them as they are and loves them as is--the more prone they are to fall prey to someone who would strip-mine them of their faith and energy and emotion and leave them hanging.
Hangers on
"And no marvel; for satan himself is transformed into an angel of light. Therefore it is no great thing if his ministers (*shudder*) also be transformed as the ministers of righteousness; whose end shall be according to their works. I say again, Let no man think me a fool; if otherwise, yet as a fool receive me, that I may boast myself a little." (2 Corinthians 11:14-16)
Paul continues to do that very thing. Explaining away how he had legitimately gone through more at the Lord's leading to ensure he'd have the weight to back up his words. In the previous chapter (10:10), he retorts by way of what looks like a slight. "For his letters, say they, are weighty and powerful; but his bodily presence is weak and contemptible." In other words, you wouldn't guess by looking at him that the things you read out loud in your church months prior came out of him, were you to see him in person ("Whence hath this man this wisdom, and these mighty works?" Matthew 13:54b--speaking of Jesus). But he knows. He knows the gift he carries because not only did Jesus appear to him and temporarily destroy his vision on the road to Damascus (see Acts, chapter 9), but Paul cultivated and also excavated the gift that God had put within him when He created him. This is what we're all aiming at. And anyone who doesn't go to God, blunt as this may sound, will only have other people to look to when needing to become something.
God made you. And He wants to make you into something. Beautiful thing is, after you become aware of this fact, you can actually help Him do that very thing.