Hellooo @MindfulGal
It is heartbreaking when our loved ones begin to change in ways that are confusing to both them and us. Can I ask if yor partner is in his early 20s? The reason is that is prime time for onset and diagnosis of major mental illnesses. Getting a diagnosis from a pdoc (rather than a GP) may be wise, as depression is often a symptom and not the final diagnosis; sadly it often takes a crisis for patients to seek help.
But I deviate, your questions are can a relationship survive and how not to take things personally.
I can only speak from my experience but will deliberately start with your question of can a relationship survive? It is far more conplex than what I will go into but sadly many relationships fail, irrespective of mental illness, statistically however adding MI, the odds for success are reduced as among other things the paranoia and delusions of the unwell person involve their partner, they can withdraw socially, behaviours can be odd and the list goes on. Having said that, it is possible to have a good partnership and I remain married after 34 years, most of them happy (but some very difficult).
Most loving relationships that survive are when the patient takes responsibility for the management of their illness, involves their partner in their treatment plan and the well person treats their partner as an equal in their relationship, learns how to cope with the illness and how to manage their own happiness independent of the relationship (none of this pie in the sky 'you complete me' nonsense). This has definitely been the case fir Mr Darcy & I.
Looking back, I think we have always been the types that have encouraged and supported each other to have our own interests which probably held us in good stead when he had his mental health crisis 17 years ago. For a while there I did get lost in his mental illness; it has been a slow process and time will tell if I have not got back into some things as my priorities changed or if I am still affected by the events around his crisis (which involved an attempt, resulting in injury). Additionally we place a high value on marriage; we want to grow old with each other.
It is very much a learning curve about how not to take things personally. Caring for anyone with a chronic disorder can be a rocky road. Growing resilience, looking after ourselves and ensuring we have our own things to keep our own cup full is all important and is called 'self care'. Placing the responsibility of our own happiness on our partner is a recipe for disaster.
I will tag you in some self care threads.