Four letter word

Move on, my sea-bowned son.
Your ship has come, and this trial is done.
There's no need to stay floating amidst the doubt
Because you are no longer down and out.
Take this strength and pull yourself away.
My hand is yours for when you go astray.
Don't be angry, because i did it for your good.
Even though now you linger, like i knew you would.
Pull yourself together before you join your crew
I once owned this ship, but now it's for you.
Take it and go home, where i'm waiting through
The night to catch a glimpse you coming back.
Tired and waiting by a candle light,
I hear the sounds of an inside attack.
Try as i may, try as i might
You must learn this on your own.
And if you can make it i would give you it all
On your way back home.