Do you mean that at ten years old you remember all of your former life and could get to change things?
Moving my life back to being ten years of age would make this year 1971.
If you look at the changes that have happened since then for everyone. Computers were locked away in universities and massive corporations, no e-mail, cell phones, internet or satelitte TV.
My biggest mistake I think actually occured at about the age of eleven. I chose to remain at a secondary school with my friends rather than going to a grammar school having passed the eleven plus exam at the end of my first year of secondary school.
That mistake closed so many doors for me for so many years. I would have a chance to see what might have been if I had chosen grammar school over the friends I no longer know.