But get this: We don't use Safek Berachot L'Hakel against the teachings of the Arizal.
A cute parable regarding this principle: There's a question about the berachah we make on Rosh HaShanah, that HaShem forgives His people. How can we make a blessing as if God will certainly forgive us, even before we ask for forgiveness? Maybe we won't merit to be forgiven?
The answer lies in this story: a child really wanted an apple, but his father didn't want to give it to him, so the insistent child made a berachah on the apple, and his father was forced to give it to him. (otherwise it would have been a needless utterance of God's name) Similarly we make the blessing on Rosh HaShanah to (figuratively) force HaShem's Hand to forgive us.
ps. Someone please remind me of the source of this parable.