Which way to forgiveness?

Something that comes up again and again on the path to spiritual growth is the importance of forgiveness of one's self and of others in order to love more fully.

This is where I often get stuck. Mistakes and short comings I've made seem to hang in the air around me and acts of cruelty I've witnessed and experienced have taken up space in my heart.

What to do? I can see why it's important to make peace with these issues (or at least 'put them down' somehow) but then comes the question: why do I/we deserve forgiveness? I know their must be a door to genuine forgiveness but it feels blocked by this question...

Any advice?