First of all, please notice in verse 12 God removed the gift that God alone had given Cain to be a farmer. Then we see he became both fugitive and vagabond. Both words indicate aimless wandering.
In the Hebrew fugitive is the word nûa‛ 5128 in Strong's and is a verb meaning to shake, to stagger, to wander. It refers to a displaced person, a wanderer, a vagrant. Vagabond is from the Hebrew word nûd 5110 in Strong's and is also a verb, but more emphatically has the sense of aimless motion or actions. It refers to a person moving about aimlessly without a home.
Brethren, all of mankind is on a journey, but the curse of sin to those not under the blood of Jesus Christ with eyes on Him and the goal of the Kingdom of God, is aimlessness in motion and in action on their journey.
Not only were Adam and Eve and their progeny separated from God and removed from dwelling with Him in the Garden of Eden, they were also separated from the source of life - the Tree of Life! The tragic results are very clear there for anyone to see! God simply and clearly expounds upon the result of sin. Next we have an example involving Cain and the curse coming upon him.
He is obviously concerned. There seems to be a measure of remorse in him, at least once he found out what the punishment was going to be - separation. We also find that God does not relent from what He wills to do.