To repose in the blood of Christ is to rest in the assurance of Jesus Christ's completed work upon the cross. It's the assurance of having been forgiven for all our sins. However, this doesn't really occur until we are truly repentant and wholeheartedly desire to live our lives in the heavenly will of God. This is being "born again", or "born from above" (John 3:3).
In the eighth part of "A Plain Account of Christian Perfection", which took place about three months following his born again experience at the Aldersgate Street service, John Wesley wrote:
In August following  I had a long conversation with Arvid Gradin, in
Germany. After he had given me an account of his experience, I desired him
to give me, in writing, a definition of "the full assurance of faith," which
he did in the following words:
"Requies in sanguine Christi; firma fiducia in Deum, et persuasio de gratia divina; tranquillitas mentis summa, atque serenitas et pax; cum absentia omnis desiderii carnalis, et cessatione peccatorum etiam internorum."
"Repose in the blood of Christ; a firm confidence in God, and persuasion of His favor; the highest tranquility, serenity, and peace of mind, with a deliverance from every fleshly desire, and a cessation of all, even inward sins."
This was the first account I ever heard from any living man, of what I had before learned myself from the oracles of God, and had been praying for (with the little company of my friends) and expecting for several years.
What should be the results upon the life of a born again believer as he or she reposes in the blood of Christ? Such a person should have "the highest tranquility, serenity, and peace of mind". And if these peaceful qualities are not present in a believer's life, then there is something wrong. Something is missing. But more importantly, something remains - FEAR!
Fear is the result of imperfect love, and Christian perfection requires the inward presence of God's perfect love. Fear and perfect love cannot exist in the same place, as John tells us (1 John 4:18):
There is no fear in love; but perfect love casts out fear, because fear involves [or has] punishment [associated with it], and the one who fears is not perfected in love.
Do you remember all the fear involved with Y2K (the computer date problem associated with what would happen at the beginning of the year 2000; and the fear that the whole of society would come to a halt)? Well, many "Christians" fell into this trap, too. They feared what would happen. We witnessed these fearful people hoarding food, much of which has since started to go bad. One woman said that when she opened her stored grain container, moths flew out. If it had moths, it also had worms. This is the same thing that happened in the wilderness when the Israelites kept more manna than they required for their immediate needs (Exodus 16:20).
We also witnessed several "Christians" arming themselves in fear that the 2,500 inmates in the two local State Correctional Facilities would somehow be set free, or that "city folk" would try to steal what they had stashed away. Where was their faith? It was as though they had flushed it down the toilet along with whatever perfect love they may have had.
There is a whole "cult" within Christianity that preys upon these fears, and they do it over and over again. And, unfortunately, the same people keep repeatedly falling for the lies. This is not reposing in the blood of Christ, this is camping with the devil!
This brings us to another part of what should be seen in a born again believer's life: "a deliverance from every fleshly desire, and a cessation of all, even inward sins". From time to time, each and every one of us probably falls short of this ideal goal, but the key is that we wholeheartedly desire to live free of all sins and fleshly desires, and truly fight against such temptations.
These are the key points that both Wesley and Gradin are making. These are the inner attitudes that lead to Christian perfection. There is no such thing as "cheap grace"!