For many Christadelphians life is a constant struggle. The focus in many ecclesias is on the extreme sinfulness of human nature, and members are encouraged to attend as many meetings as they can and study the Bible so that they can "build themselves up" to resist the temptation to sin. Very often when people fall into difficulties they are told it is because they neglected attending meetings, or didn't read the Bible often enough. While this has the positive effect of producing a community of people who know their Bibles quite well it also has the negative effect of generating further guilt in people who are already struggling. It also perpetuates the error that the struggle against sin is something a Christian has to do through their own efforts.
The passage I quoted earlier from Hebrews 6:4-6 is often interpreted by Christadelphians as having no relevance for Christians today, but applied only to first century belivers. "It is impossible for those who have once been enlightened, who have tasted the heavenly gift, who have shared in the Holy Spirit, who have tasted the goodness of the word of God and the powers of the coming age, if they fall away, to be brought back to repentance, because to their loss they are crucifying the Son of God all over again and subjecting him to public disgrace."
There are two major problems with this Christadelphian interpretation:
(1) It is wrong. Many Christadelphians deal with "difficult" passages in the Bible by saying that they applied only to the first century, but they have no systematic way of knowing how to determine which passages are first century specific and which have universal relevance. The only "rule" seems to be if it doesn't fit in with Christadelphian teaching then it must be first century specific.
(2) The struggle against sin is a struggle between believers and their own human natures and human nature is invariably the winner. (Some Christadelphians even teach a doctrine of "the inevitability of sin", saying that it is impossible to overcome sin). According to Christadelphian teaching God is a by-stander - He observes His people struggling but doesn't get involved because this would be to take away their free will and turn them into "robots". However, the overwhelming emphasis of the New Testament is that the struggle against sin is fought by God for the benefit of His creation and He enables His people to overcome so that they are "strong in the strength which God supplies".
Hebrews 6 teaches that God provides a "heavenly gift" which is a "taste" of the "powers of the coming age", the Holy Spirit, to those who have been enlightened. By denying this present involvement in the lives of believers, and God's empowering of His people, many Christadelphians (although not all) not only deny the provision of the Holy Spirit to aid and enable Christians to overcome sin, they also by implication deny that they have been "enlightened".
However, Scripture provides a wonderful promise that those who call upon the name of Jesus will not only be saved in the age to come but they will also have access to all the resources of heaven to enable them to be victors in this world too. It is a promise that God will provide all we need for our spiritual growth. To any Christadelphians reading this I want to encourage you to embrace God's promise, accept His free gift, and discover that there is no condemnation to those who are in Christ, because He sets us free from sin and death (Rom 8:1-2).