why not go for broke?

A question to think about:

The gemara (Baba Basra 147) writes that if the first day of Rosh haShana is hot, it means it will be a warm year. If it is cold, it means the year will be a cold year (sounds just like Farmer’s Almanac). The gemara asks, “L’mau nafka minah?” What difference does it make? The gemara I guess did not have a heating oil futures market to invest in, so the gemara says the nafka minah is for the tefilah of the kohen gadol on Yom Kippur.

Rashbam and Tosfos explain as follows: if it’s going to be a hot year, then the kohen gadol should daven for it to be not so hot; if it’s going to be a cold year, he should daven for it to be not so cold.

I don't understand.  Why not go for broke and ask for more?  I was reading a book recently and one of the characters is always telling his friend his wishes, like he wishes to be paid decently for his work that day so he can take off the next day.   His friend in turn always wonders why if he is wishing, he doesn't just wish for more -- why not wish for enough money that you don't have to work at all?  There's no limit on wishes.  I am bothered by the same thing here.  You can ask Hashem for anything.  Why accept that it’s going to be a hot year and just Hashem to make it a little less hot, or vica versa, when you can ask Hashem to make it seasonable, or whatever temperature you want? 

Whatever the answer to that is, one other point about tefilah: I saw R' Chaim Kanievsky quotes from the Chazon Ish that even though normally on Shabbos or Y"T one cannot make personal bakashos in tefilah, Rosh haShana is an exception.  I don't know the makor for such a din, but apparently the Chazon Ish said it.  So IY"H we should all daven for whatever we need (and the first thing to daven for I guess is that we have the brains to realize what we really need) and hopefully your tefilos and my tefilos will make a difference and we will all have a kesiva v'chasima tovah.