I think growing old in 1900 is diff from growing old in 2020. I don’t think these are experiences that translate well over time and place.
‘What advice would I give my younger self’ also doesn’t compute. Because that would mean that I would end up with entirely different life experience and the person giving the advice would not exist as they would have changed. In sci fi, this would be the classic causal loop/temporal paradox time travel dilemma.
If this is about health, you are better off obtaining a DNA report and go through the high risk illnesses you have inherited with your physician. I did this and was able to identify a few things missed by my previous maternal units. Some of them probably died because one mutation was undiagnosed.
From a dietary perspective, follow the grandmother diet. Eat what your longest living ancestors lived. It helps if you haven’t migrated far off.
P.S: Don’t rely on dna ancestry reports migrations. I am South East Asian and ancestry report suggested that I had a Finnish ancestor. I doubt if I can follow the Sami diet. In California. So there is that...
My suggestion is to draw a family tree for upto 4-7 generations. 7 is ideal but would be tough for most.