The pasuk (26:7) reports our crying out to HaShem during the slavery in Egypt. However, the pasuk does not say that HaShem heard our prayers, but rather ‘HaShem heard our voices.’
The Chofetz Chaim remarks from here that it is the ‘mere’ crying out in times of trouble/danger that is accepted. And, the Chofetz Chaim adds, the main thing is to daven for the nation (not just for yourself) and to do so immediately after one has performed a mitzvah,
hence. the harachaman requests which we make after Birkas Hamazon.
