Sometimes, our enemies are highly visible in the forms of actual people. The often venomous dialogue between other faiths and philosophies has made the whole Question into something of a joke. Sometimes its not an actual attack in terms of argument or aggression, but an offer to Sin; extramarital sex or other sins of impurity, or becoming enraged. Peer pressure is a powerful force that can push us to break laws both Moral and Material.
Other times, our enemies are more insidious. If you suffer from the Sin of Lust, an unmonitored internet connection or a quiet private moment can be potent enemies. If you are prone to Rage, the news can stir you into a froth. If you have problems with Gluttony, you will have a hard time in the kitchen... and so on. Opportunity can be an enemy.
God is our primary defence against Sin, because He wants us to love Him, as He loved us before creation. Staying on the Way to the foot of the cross is a challenge that tests our will and our righteousness. A piece of Gregorian Chant, rendered to English, has long been a favourite of mine. It reads:
The mouth of the righteous speaks wisdom, and he thirsts for Justice; the Law of God is in his heart, and his footsteps shall not falter.The first commandment is that God is the Lord Our God, and we shall have no other gods before Him. These other "gods" may not be deities, but they are the things we put before God in our daily lives. We are all called as Christians to grow in our faith.
As a Catholic, I've had the good pleasure to be introduced, just over the last few months, to dozens of different devotional practices, and I've seen how diverse and personal Prayer really is. Whether you prefer to say the Rosary or the Divine Mercy Chaplet, to sit quietly in Adoration at the chapel or to meditate on the Word in Lectio Divina, there is a way for you, within your tastes, to move closer to God through prayer and contemplation.
Most importantly of all, however, is to understand what God wants of us. To recognize an enemy, we must combat his arms. When I started on this journey, I disagreed with the Catholic position on many points, and spent a lot of time in the wings, learning about other Christian denominations and their faith. It wasn't until these positions were explained to me in terms of the Human Condition that I realized I agreed with these tenants. Everything from the communion of saints, to the high position of the Virgin Mary, to confession, and the church's position on matters of sexuality were reversed.
It was not an overnight process. It took careful study. Study of the doctrine, really understanding it, is what helps us to obey it. Knowing God's laws makes us closer to God... and in that way, a proper formation of the faith is Prayer in and of itself. Read, watch, or listen to apologetics, to catechism. Only in that way, may we begin to understand the Way.
Avoidance of Many Sins is itself a form of mortification, if only in a secular sense. We have to give things up. Examining our conscience to find the things we have done takes time, for one thing. Prayer takes time, more or less of it, depending on your prayer life. Once a week, we are called to give over entire days to rest and prayer. Those of us who find a sort of self-righteous indignation in being angry are called to give up their very anger. We are to forgo the modern trend toward promiscuity and even deny ourselves pleasures lawfully obtained.
We have to remember, though, that Sin is, in a strange way, something to be loved. It is a message from our Divine Father. While we may not like to be thus restricted, it is nothing more than a parent guiding its child to becoming a better person.
We must study. From there, prayer and faith will flow.