How do you deal ? Really going through it -6 months without him

Military wives especially you can relate I’m sure and I need all the advice I can’t get. My man is leaving for 6 months not for the military but for a job that is 16 hours away on a boat. It is 6 months on and 6 months off. He is all I have here where we live and I can’t help but be super fearful of the distance. I love him so much and trust him to the fullest I just can’t imagine being able to sleep even one night without him. That’s my best friend, my everything. I don’t have too many friends here, mostly all my friends are in my home town which also pretty far away (8 hours) I just don’t know how to get through it with positivity, I try to be encouraging I just want the time we are away from eachother to be not so stressful and upsetting. He keeps reminding me he is doing this for us because it is a good opportunity/ money. I am just so scared but not sure what I’m scared of, I just don’t know how to be okay 6 months without my best friend. Can anyone give me good advice on how to get my feelings in check and things I can do while he’s gone to make it easier... I will be able to talk to him at least once a day but I hardly know anything about this job but that he has to sleep on a boat which to me is scary... ugh just need some uplifting words because he is leaving next Friday and I don’t think I can handle it...I’m trying not be selfish as nobody else wants him to go but he believes in it so i am trying to believe in it as I very much so believe in him because negativity is going to bring him down.Help.