The energy of the Spiritual Sun, just like the physical sun, comes in many types, many frequencies.  Some of these energies are positive and some are negative.  Some are beneficial and some are helpful.  Some stimulate spiritual growth and others prevent it.  
    So it is not enough to just absorb energy from the sun, you need to absorb the beneficial frequencies far more that you absorb the harmful ones.  It’s a lot like proper nutrition.  An occasional piece of cake won’t be a problem if you mostly eat healthy fruits and veggies. 
    So when taking in sun energy, our frequencies affect what energies we absorb the most.  If we are positive, loving, tolerant, joyful, we will absorb mostly the positive and beneficial energies.  If we are grumpy, stingy, jealous, intolerant, etc., we will mostly absorb the harmful ones.  
    That is a somewhat simplified explanation of how it works.  The specifics for each person is something to discuss with your spiritual teacher.