This game is MUCH easier than its previous game (Ratchet and Clank 2) about how your health is shown. This gives you a simple numerical XX/10 readout. You start with 10 health units, and quickly built this up over time. Every time you slay something you gain experience, and each time your experience bar becomes full, you get another unit of health. So soon you will have 20 units of health to work from. The more you fight, and replay levels, the stronger you will become.

Ratchet and Clank 3 - Up Your Arsenal Walkthrough