to get by/along; to contrive; to swing; to shift for oneself; to look after oneself; to take care of oneself; to fend for oneself; to manage (on one's own/by oneself)
He'll have to manage (by himself)!; He'll have to sort it out for himself!
Don't worry, I'll manage somehow!
He's old enough to look after himself!; He's old enough to fend for himself!
Up-and-coming; resourceful