Not a condition but rather a warning. Paul was not telling them that they could be damned, or that it was even possible for them to lose their salvation.
He was warning them. It is just as if I said, "if you play in the street you will get hit by a car."
It is a warning, not an assumption that now you will go and get hit by a car.
To follow your train of thought would make Paul out to be a rather confused man, and the Holy Spirit a contradictory speaker, for the rest of Romans 8 speaks of the inability of a Christian to lose their salvation.
Rom 8:28 And [b]we know that all things work together for good to them that love God, to them who are the called according to his purpose.[/b]
Rom 8:29 For whom he did foreknow, he also did predestinate to be conformed to the image of his Son, that he might be the firstborn among many brethren.
Rom 8:30 [b]Moreover whom he did predestinate, them he also called: and whom he called, them he also justified: and whom he justified, them he also glorified.[/b]
Rom 8:31 What shall we then say to these things? If God be for us, who can be against us?
Rom 8:32 He that spared not his own Son, but delivered him up for us all, how shall he not with him also freely give us all things?
Rom 8:33 [b]Who shall lay any thing to the charge of God's elect? It is God that justifieth.[/b]
Rom 8:34 [b]Who is he that condemneth? It is Christ that died, yea rather, that is risen again, who is even at the right hand of God, who also maketh intercession for us.[/b]
Rom 8:35 Who shall separate us from the love of Christ? shall tribulation, or distress, or persecution, or famine, or nakedness, or peril, or sword?
Rom 8:36 As it is written, For thy sake we are killed all the day long; we are accounted as sheep for the slaughter.
Rom 8:37 Nay, in all these things we are more than conquerors through him that loved us.
Rom 8:38 For I am persuaded, that neither death, nor life, nor angels, nor principalities, nor powers, nor things present, nor things to come,
Rom 8:39 Nor height, nor depth, nor any other creature, shall be able to separate us from the love of God, which is in Christ Jesus our Lord.