There is actually little biblical or historical support to say conclusively that the doctrine of loss of salvation is wrong. The notable figures of the early church, all believed that a person , once truly saved, could end up in hell fire. For this reason, this view is maintained by the Orthodox, Catholic, and mainline Protestant faiths. That's the result of my personal study into the historical aspects of these doctrines.
It helps to realize that God wants to partner and join with man. So that it is not a man-only effort, or a God-only effort, but both living together. It is about two people, living as one. With this in mind, although there are some exceedingly great and high promises to us, these things only become a practical reality to us if we apply and meet the conditions. God designed it in this way, because He does not want mankind to living independently of Him. Regarding being new creatures, note that it is conditional upon "if anyone is in Christ". What does it mean to be in Christ? It means to abide in Him (John 15). It means to walk in the Spirit (Romans 8:1). Ephesians 4:22-24 says we are to put on the new man. It is not guaranteed that we are a new creation just by believing, we must put off the old and put on the new. How do we do this? 1 Thess 5:19 - pray continually, thank, rejoice, at all times, do not quench the Spirit. To abide in Christ, to live and walk in the Spirit, means to have our living, our habitation in God (Col 3:2). If we don't do this, we will live in our flesh, and we open ourselves to condemnation, and note what it says:
5 Those who live according to the flesh have their minds set on what the flesh desires; but those who live in accordance with the Spirit have their minds set on what the Spirit desires. 6 The mind governed by the flesh is death,but the mind governed by the Spirit is life and peace. 7 The mind governed by the flesh is hostile to God; it does not submit to God’s law, nor can it do so. 8 Those who are in the realm of the flesh cannot please God.
So we see that salvation depends upon whether our mind is ruled by our flesh or by the Spirit. This is not automatically guaranteed after we believe in Christ. From experience it takes time and it takes effort.
Hebrews 4:11 says we must strive to enter His rest. It means we have to work hard. We have to work hard at doing those things Paul instructs the church: pray, rejoice, thank, grieve not the Spirit, etc. This is God's will for us (1 Thess 5:18), because it results in us abiding in Christ, living in the Spirit. The best part of your paragraph was this one: "But God showed me His great love". I think God doesn't really care if we do or don't believe we can lose our salvation. He wants to show us His great love. He wants us to know Him better. Perhaps the reason why you once thought you could lose salvation, was so that you could turn to Him out of frustration or fear, and experience His great love. Perhaps your conscience condemned you, you experienced self-condemnation. But then you learnt the secret of turning to Christ and abiding in Him by setting your mind on the Spirit. Although God brought you out of Egypt (saved you from sins), you needed this desert experience, so that you could enter His rest. And once we enter His rest, we don't particularly care if such and such a doctrine is right or wrong, we are just happy to abide in Christ. That is the important thing here. We can rest in Christ if we have set our mind on the Spirit and abide in Him (see my previous comments and Scripture). If we abide in our flesh, there is no rest, no peace, no joy, no contentment, no experience of life. Daily and regular confession of sins is important to maintain a healthy fellowship with the Father. God wants us to do good works "in Him", they are necessary for us to obtain rewards, and though they may not affect our own salvation, they can affect the salvation of others. If we are concerned about whether we will make it or not in the Christian life, a great encouragement is that Jesus is praying for us that our faith will not fail Romans 8:34, Luke 22:32.
In summary, the security of our salvation, does not depend upon us believing a certain doctrine, it depends upon us abiding in Christ (living in the Spirit), as a result of our continual prayer, thankfulness and careful consideration of the Holy Spirit within us. If we abide in Christ, we have THE doctrine, and there is no such thing as a "dangerous doctrine". He is the way, He is the truth, He is the life. Any doctrine apart from Christ, is not the way, or the truth or the life. So a dangerous doctrine, is to live a life without Christ. The safest place to be is in the centre of God's will, and the centre of His will is found in the person of Jesus Christ.