This is a common misunderstanding and one reason we Christians need to better understand God's Word if we are going to use it properly (2 Timothy 2:15).
The book of Proverbs explains it's purpose in 1:1-6 as Solomon's collection of wise sayings to give wisdom and instruction, "for understanding proverbs and parables, the sayings and riddles of the wise."
The book of Proverbs is God's Word, so we must trust its explanation of its purpose and not go beyond it.
Some Proverbs are promises, but only those which are also found as such in the New Testament. For example, Proverbs 3:5-6 is a promise (see Hebrews 11). But many Proverbs such as Proverbs 10:22,27 are not promises of God.
Why is this important to understand? Because using some Proverbs as promises misleads people, confuses them and makes God look like a liar.
~I know that many of you have been taught that Proverbs are promises because I see this misunderstanding often expressed in Christian materials, especially regarding Proverbs 22:6, which is not a promise but a generalization. It can be hard to let go of certain teachings when we want them to be true or when we haven't seen adequate proof that they aren't Biblical. If you are having difficulty with this devotion, I encourage you to read a more thorough post I wrote called "Proverbs Aren't Promises."
But don't take my word for it, also check out these articles by ministries and men with far more education and training than my own:
Richard Pratt of R.C. Sproul Ministries
James W. Mohler of Biola University
Got Questions Ministry
Focus on the Family
John Piper Ministries
Linked to: Modest Mom, Whole Hearted Home, A Wise Woman, and Imparting Grace.