How typical is it that a change in medications produces what appears to be a complete turn around?

over ten years ago my husband had very drastic surgery involving removal of esophagus and part of his stomach. He was put on heavy duty pain meds (opiods) and anxiety meds and went into a downhill spiral. Several times he had his meds changed with fewer and fewer pain meds, but still takes them. Back in May of this year he had a terrible episode of dementia that I couldn't handle, and we went to the MD where he said happily that he was getting better and better. I met with the MD in the hall and recounted the episode he'd just had, and immediately he ordered fewer meds and a MedPak.
Since then, for 4 months since, there's been this turnaround! We can converse intelligently, and he's even helping around the house (for the first time in 10 years).
Now my problem is myself. After years of caregiving with one ear always open for sounds that I must help, I spiraled into a deep depression. I could barely get out of bed in the morning. I wondered if maybe the reason this happened is because I had carefully made Pans A to D as I was told by 3 doctors, including a neuro-psychologist, that things were only going to get worse and I would someday need to place him into a facility.
I think I've managed to deal with my depression, but I still fear the future. How can I buffer myself from a possible retreat? And is it a certainty that he will go back to his symptoms? The incident that raised the alarm was, in part, finding him urinating in a dresser drawer, thinking he was on the toilet. He has no memory of any of the things that alarmed me in the past ten years. Should I let him read my journal so he knows, while he is acting competent?