Personally I love the feeling as I relax more and also I am reassured that if I have an unexpected accident then at least I can Rely on the diaper/nappy to keep me dry,
I have to occasionally wear them as a middle aged adult in his 44th year of life, and that's mostly because of the fact that I have a unpredictable/intimittant problem with my bladder control.
However when I am in diapers I feel safe and care free like I once did as a child all those years ago, and in particular I love the familiar feeling of the bulk between my legs and the soft coshioning of the inner padding and the warmth on a cold night as it keeps my bottom half of my body comfy.
I also sleep well when diapered something that relates to my inner child, in the fact that I never really grew up for various reasons that where either beyond my control or for deep rooted psycallogical causes plus I have PTSD,
not from being in combat or being a first responder but because I suffered years of bullying and torture right from my preschool years until I was a adult by different monsters, however this thankfully was not from my pearents or relatives as I seemed to be a magnet for bad people in life.
So wearing diapers is a way of healing myself from past traumas whilst safely regressing back to a time when everything was more simple and innocent, I hope this helps awnser your questions.