What is the difference between guarding your heart and your mind?

In proverbs 4:23, we are told we should guard our hearts because it is the wellspring of life.  According to dictionary.com, a wellspring is "the original and bountiful source of something."

In Philipians 4:7, we are told "the peace of God will guard your heart and minds." 

What is the difference between guarding our hearts or minds?   How do we know when we are guarding our heart or our mind?  It seems that our hearts are where our dreams, desires, motivations and zeal for life are kept.  Our hearts are the driving force behind what we do, what we say, where we go and how we relate with one another.   To guard our heart would mean not to get discouraged, but to feed our hearts with God sized thoughts and actions.  Verses that are "heart healthy" are, "For I know the plans I have for you declares the Lord.  Plans to prosper you and not to harm you.  Plans to give you hope and a future."  Jeremiah 29:11 and "For the spirit God gave us does not make us timid, but gives us power, love and self discipline."  2 Timothy 1:7  What are some examples of spiritual junk food that may be harmful to our hearts?

To guard our minds seems similar to guarding our hearts.  Some may suggest guarding our heart and our mind would be guarding the same entity.  Psalm 119:11 states "I have hidden your word in my heart so that I might not sin against God."  At first glance, I thought this verse was referring to the memorization of scripture causing one to believe the mind/heart is where this type of activity occurs.  However, taking a second glance, I realize the word has already been memorized...it is being stored in the heart.  Luke 10:27 states to "Love the Lord your God with all your heart, soul and mind."  The mind and heart are written as separate entitities in scripture which means they have different spiritual purposes.

If the mind is a separate entity from the spiritual heart, I would imagine the mind represents the analytical and data gathering/remembering aspects of our existence.  It is with our minds that we work out problems, make decisions on the best options depending upon what makes most sense, memorize information and contemplate our being.  With our mind, we memorize His word and then we feed those thoughts to our hearts.

To guard our minds would mean to focus on the truth.  I believe to love the Lord with all our mind means to work toward learning and growing our thought processess as much as possible.  If we guard our mind, we keep "spam" from getting through our mental filters.  We fill our minds with powerful information that leads us to greater understanding.