The "this" was "can be a big distraction if you are trying to create something". Or, put more clearly, 12 year old boys need to understand that (1) it is getting time for them to start to take the rest of their life seriously, (2) for that seriousness, it is time for them to get into some hard work learning and doing, (3) being 'creative' eventually is important, and it is not too soon to get started, (4) for this seriousness, getting much involved with females can be a distraction from a little bit with little harm and maybe some benefit up to too much and a lot of harm.
Ok I see what happened. When I read the statement for some
reason I missed the comma.
So I read it like
"12 year old boys believe this!!!" (mocking)
rather than
"12 year old boys need to understand this!!"
Good points and the inverse is true for women. My sister spent much of high school being popular and although she was smart (and later got a Masters) she didn't achieve as much as she could have had she not been as popular and attractive and good personality. No question in my mind about that.
