I personally feel that we know in theory what to do but how do we put this into practice?

I think what you said is a very true thing. We may know things in theory but it is difficult to practice. It is because of this issue, that I said at the end about prayer. No one, not me or you or any body can put these things into practice without the help of God. We need to constantly depend on God. The Bible offers us divine assistance and promises regarding this aspect. I'll give you a couple of encouraging verses

1. Gal 5:16 - Walk by the Spirit and you will not gratify the desires of the flesh

- It means that you cannot bear these good qualities on your own - and the good news is God says its when we walk according to the Spirit that we can bear the fruit of the spirit. How can you walk in the Spirit? You can do that by making God the main influence in your life. Read His word, pray, spend time in good fellowships. Do things which are spiritually nourishing.

2. John15:5 I am the vine; you are the branches. Whoever abides in me and I in him, he it is that bears much fruit, for apart from me you can do nothing.

- Abide in Jesus - again by being close to Him - draw your spiritual lessons from Jesus - remember that you cannot do anything without Jesus. Sometimes we are not able to practice these lessons because we try to bear fruit by living an average spiritual life without regular bible reading and prayer.. Remember to see your bible reading and prayer times and fellowships as times that will nourish you, and take it seriously! It helps. As humans, we have the tendency to be pretty casual about these things. So invest time to remind you these truths

3. 2 peter 2:3 His divine power has granted to us all things that pertain to life and godliness, through the knowledge of him who called us to his own glory and excellence

We are given all the divine power to live a life that God wants us to live. God never rejects our good desires to live a life pleasing to Him. So keep persisting in prayer, about the personal struggles you have in living a pure life. The devil may come and tell you to stop praying and that it is not of much use and you cant live a holy life and it is part of your nature.

4. 1 Thess 5:23 Now may the God of peace himself sanctify you completely, and may your whole spirit and soul and body be kept blameless at the coming of our Lord Jesus Christ. He who calls you is faithful; he will surely do it.

So don't be discouraged - God is working on you! Remind yourself this great truth. This big God - our heavenly Father is interested in keeping you holy. He will sanctify you completely. He is watching over you so that one day you will be perfect like your Heavenly Father. God is faithful to do it! And it is a great thing to commit your life to God's hands and persist to live a Godly life by depending on Him.