As a middle age (or slightly older 
) person, I would say such advice given by “few older friends and relatives” is meant to be well meaning because they care about you and want you to benefit from the knowledge they’ve gained and prevent you from making mistakes that they might have made at your age. I seriously doubt it is intended with any malice, lack of self-esteem, or bullying. If they didn’t give a rat’s patootie about you, it would be easier to keep their mouth shut. (ok, we all know a few who pontificate for the sole purpose of hearing themselves talk but I don’t think that represents the majority of people)
So, listen to what they say, nod, and smile. There’s a chance there might be a nugget or two of helpful info in there. If not, in one ear and out the other. Better to be less cynical about other people’s intentions. People in general like to be helpful. No more, no less.