Passage
And straightway they left the nets, and followed him.
And straightway they left the nets, and followed him.
Mark 1:16 And passing along by the sea of Galilee, he saw Simon and Andrew the brother of Simon casting a net in the sea; for they were fishers.
Mark 1:17 And Jesus said unto them, Come ye after me, and I will make you to become fishers of men.
Mark 1:18 And straightway they left the nets, and followed him.
Mark 1:19 And going on a little further, he saw James the [son] of Zebedee, and John his brother, who also were in the boat mending the nets.
Mark 1:20 And straightway he called them: and they left their father Zebedee in the boat with the hired servants, and went after him.
The verse centers on "straightway", "left", "nets", and "followed". It is saying that the verse draws attention to "straightway" and "left", so its meaning should be read from those terms before moving to application.
The nearby context moves from verse 17's "And Jesus said unto them Come ye..." into verse 19's "And going on a little further he...", so "straightway" and "left" belong inside that flow. In Mark context, the local focus is Christ, faith, and discipleship.
A plain takeaway is to answer the verse's own emphasis on "straightway" and "left" with trust shaped by these words, not by a vague optimism outside the passage.