This article is from the PGP FAQ, by Jeff Licquia firstname.lastname@example.org with numerous contributions by others.
With conventional encryption, you can read the message by running PGP
on the encrypted file and giving the pass phrase you used to encrypt.
With regular encryption, it's impossible unless you encrypted to
yourself as well. Sorry!
There is an undocumented setting, EncryptToSelf, which you can set in
your CONFIG.TXT or on the command line to "on" if you want PGP to
always encrypt your messages to yourself. Be warned, though; if your
key is compromised, this means that the "cracker" will be able to read
all the message you sent as well as the ones you've received.