Snakes preying on frogs is a normal food chain, which is essentially normal and has no effect on frog population. Don't worry, of course, you can commit suicide if you can't bear it, because it has no effect on the biological chain.

Of course there are exceptions. For example, if one of the frogs and snakes here is an alien invasive species, it is better to kill it, because this situation is naturally uncontrollable.