Friendship is like a string, when it breaks, it may be tied again but a knot comes there at the joint. So be careful about your friends and never try to break your friendship because it may be made again but there will be bad impression of break is left in the string of Friendship
How 2 grow friendship? pick a good heart, plant in a pot of trust, water with good thoughts, add some emotions and faith, remove the misunderstanding and nourish it.