Every rejection (or ignored query) takes you one query closer the acceptance.

My ongoing belief is that there is one agent out there who will love my work and sign me up, and querying is merely the means I use to find him or her.

I have no interest in self-publishing - I am traditionally published by a small publisher, with a new book coming out in August - but I will keep querying until I get an agent who can help me climb up the writing ladder.