"Ship" "Sailing" are part of a ensemble of ideas/idioms in English.
A very common expression is "that ship has sailed." For example, someone asks you "I know it's late to invite you to my party tomorrow night, but could you come?" You can answer "That ship has sailed." meaning it's too late to try and change my plans now, they are already "set in stone."
"My ship is sailing" would be similar. It refers to the image of a ship sailing, that is, something that has already left the port, and cannot be called back. So it speaks of commitment. You are committed on a path that cannot now be changed. Similar to being on a train that has left the station, its course cannot be altered.
Learn hard, think free!
Alan.
[yes, I am an English teacher, and I *do* know that "hard" and "free" are adjectives, rather than adverbs, following a verb. Hey, that's the reality of modern day English. As the Borg are so fond of saying, "Resistance is futile."]