Every Christian must be thoroughly convinced that his spiritual life can in no way be viewed as the quiet unfolding of an inconsequential life without any problems; rather it must be viewed as the scene of a constant and sometimes painful battle, which will not end until death — a struggle against evil, temptation and the sin that is in him.
We must at the same time affirm another truth […] It is that the Christian life is a combat, a war without mercy. Saint Paul, in a letter to the Ephesians, invites us to put on the armor of God to fight not against human enemies… but against the cosmic powers of this dark world and the spiritual forces of evil in the heavens (Ephesians 6:10-12) and he details all the pieces of armor that we must put on.
Every Christian must be thoroughly convinced that his spiritual life can in no way be viewed as the quiet unfolding of an inconsequential life without any problems; rather it must be viewed as the scene of a constant and sometimes painful battle, which will not end until death — a struggle against evil, temptation and the sin that is in him. This combat is inevitable, but is to be understood as an extremely positive reality, because, as Saint Catherine of Siena says, “without war there is no peace”; without combat there is no victory. And this combat is, correctly viewed, the place of our purification, of our spiritual growth, where we learn to know ourselves in our weakness and to know God in His infinite mercy. This combat is the definitive place of our transfiguration and glorification.
Source: Searching for and Maintaining Peace (Amazon Affiliate)