You might also want to store your spirits in the freezer. That way the ice and booze are at the same extremely cold temp. As you shake your mixture with ice you get nice little shards that make for a bracing concoction.
Also, after many years of experimentation, I have discovered that my limit is precisely one martini.
One is the perfect number, because 2 is too many and 3 is not enough.
“If you can do 3, you can do 30.”
Works for Tequilla & Gimlet shots too.
For the record, my general limit is two martinis and rarely do I exceed that. As Dorothy Parker once wrote:
"I love to drink martinis, two at the very most, after three I'm under the table, after four I'm under my host..."