[OTR-users] Perfect Forward Security

[Jason Cohen]

Quoting:

The keysize of the DH only has to be large enough that you're
  comfortable with the adversary having to break a DH key agreement *per
  message*, since (approximately) each message you send is encrypted
  with a new key, derived from a fresh DH key agreement.

If an adversary steals your private key and can break one message, don't they have all the needed information to decrypt the next message? They have the key used to encrypt the next message as well as the private "x" value. I'm probably just confused. I would appreciate it if someone could clarify this for me.

Jason