I like what Matthew Henry says about this verse:
Modesty is the badge of wisdom. He that is truly wise hides his treasure, so as not to boast of it (Mat 13:44), though he does not hide his talent, so as not to trade with it. His wisdom rests in his heart; he digests what he knows, and has it ready to him, but does not unseasonably talk of it and make a noise with it.He then goes on to observe that foolish people invent occasions to "tell what they know" instead of letting it rest in their heart, like the wise person above. They go to great lengths to guide the conversation into an opening for revealing their tidbit of information.
The wise person in the first portion of the verse brought Mary to mind. The Scriptures tell us that after the angel revealed her destiny to her, "She kept all these things and pondered them in her heart." (Luke 2:19)
Wisdom rests in the heart . . . I was reading in II Corinthians, where Paul talks about the power of Christ "resting" upon him. The word there is a slightly different one than that used in Proverbs -- this one carries the meaning of dwelling, or residing in, a place. I would like to think of wisdom residing in my heart, wouldn't you? I get uncomfortable talking about myself, so boasting is a little foreign to me. But Paul actually said that there is one thing that we can boast about:
Galatians 6:14 But God forbid that I should glory, save in the cross of our Lord Jesus Christ.
Now, please don't get me wrong --- I'm not saying to get all puffed up and proud, and strut around! Just sayin' that all of our gifts and talents are just that: gifts from Him, that we should be good stewards of. We live and breathe due to His mercy and grace, so if we are going to point to something that we really should be rejoicing about, it is the cross of Christ that saves us!