THIS ISN'T NEGATIVE..
As someone who has gone through the ringer with a relationship; in part due to work. I can honestly say it doesn't always get better. What does happen is that partners learn to understand and make adjustments for the ones they love. As already mentioned, there is a lot of psychological impacts with shift work specifically and also due to lack of sleep.
As Train Drivers, as well as others in similar situations, we are a little psychologically broken. If I went through my week, I could list all kinds of weird and stressful situations. My, now ex partner, never used to understand that when I come home I want to switch off and not think about it. I need a decent nights sleep and a partner who understands I'm gonna be Mr Grinch at times and sometimes I don't want to share that I almost killed someone due to a near miss or I almost stopped short because I drifted off thinking about the kitchen for the umpteenth time. I can't go to your Mother in laws birthday, not because she's the Devil, but because I need to get up at 0300 to drive a Choo Choo at 0434. If you can understand and take the rough with the smooth; I swear I will love you forever. Seriously, it often takes a very understanding and committed partner to be with a Train Driver; or generic Shift Worker.
The smooth really does have its benefits. Long weekends and being able to hit the shops during the week; avoiding the 9-5 crazy weekend mentality. Higher wages (Kerching !!!!) and the benefits that brings. I have had many benefits that have outweighed the hard parts of the job. I think maybe, your partner needs to also understand this part too. (open to any PMs)
My kids have been on the better side as they have grown up only knowing I'm a Train Driver so they generally understand that I might not be there for everything but I'm there for quite a lot; again, the money helps (little B'stewards

) Kids are a little more resilient than adults as their expectations are a little different and I do understand that mine grew up with me as a Driver but others have had the culture shock; and that is important to recognise.
I've met many 'Driver Wives' over the years and it truly does take a special kind of person to love us grumpy buggers but it IS worth it in the long run.
20yrs in and I'm still a miserable git when I've had a long shift/week/day/trip/assessment/shunt/etc.