1. a high or inordinate opinion of one's own dignity, importance, merit, or superiority, whether as cherished in the mind or as displayed in bearing, conduct, etc.
2. the state or feeling of being proud.
3. a becoming or dignified sense of what is due to oneself or one's position or character; self-respect; self-esteem.

So often people move from a becoming or dignified sense of pride to a high or inordinate opinion of themselves. They fool themselves and lose the respect of others. It is possible to confident of some things, such as the Law of Universal Gravitation - drop an apple and it falls.  The same thing with an orange.  However, being confident of this law does not give a person reason to be proud that they are right about what happens when they drop things. But other things are more a matter of opinion and although we might be confident that we have arrived at the correct opinion of a matter there is, again, no grounds for pride in having done so. Such pride is unattractive and unbecoming. A peculiar example of this is when some people claim to have "gay pride".  This makes as little sense as someone else claiming to have "heterosexual pride".  Whichever opinion on sexuality we arrive at it is nothing to be proud of.