1 Cor 12:14-17
14. For if I pray in an unknown tongue, my spirit prayeth, but my understanding is unfruitful.
15. What is it then? I will pray with the spirit, and I will pray with the understanding also: I will sing with the spirit, and I will sing with the understanding also.
16. Else when thou shalt bless with the spirit, how shall he that occupieth the room of the unlearned say Amen at thy giving of thanks, seeing he understandeth not what thou sayest?
17. For thou verily givest thanks well, but the other is not edified.
Paul uses the body as an example of how important each body part is. The whole body will be impaired if an 'unimportant' part thereof is removed. If you think that your gift is more important than other's, then you are spiritually proud.
We are not allowed to look down on people who are apparently unimportant, and we're also not allowed to be jealous of people who received impressive gifts. No, we must rather use the gifts we have received, and encourage others to use theirs as well. If we don't do this, the community of believers will be much less effective.