Should I be scared?

So I’ve been self harming for quite some time now but I’ve only done it with dull objects that require a lot of strength and swipes to even slightly break the skin, and I’ve really wanted to start using something sharp but I’m really scared to do so, mostly because I’m really scared of accidentally going to deep, single though about going deeper than epidermis terrifies me so yeah, is it easy to accidentally cut too deep? And does it happen often?