I cannot promise you that                      I will not change
I cannot promise you that                      I wiil not have different moods
I cannot promise you that                      I will not hurt your fellings anytime
I cannot promise you that                      my faults will not be visible

But

I do promise you that                           I will always be supportive to you
I do promise you that                           I will share my all feelings with you
I do promise you that                           I will be completely honest with you
I do promise you that                           I will cry and laugh with you

But
Most of all I promise that I WILL LOVE YOU FOREVER.