Overdose on benzodiazepines is actually quite rare provided they are not mixed with other CNS depressants (I met a girl in the ER one day who had eaten 40 Rivotril 2 mg tabs (Klonopin in the US - thats 80mg of clonaz, a butt load of clonaz) and they just monitored her until they wore off).
With that in mind, there are some risks, yes, so maybe if you take clonaz, first do so
with someone around to see how you tolerate the medication; not everyone is going to have a Dr.