trigger AFTER INSERT

Hi,

I think that I have a conceptual problem and I hope anyone could help me.

If I write a trigger AFTER INSERT and I have one error in this trigger, the
record (that I think was already inserted) is not inserted.
Example:

INSERT INTO tableX <record1>
trigger sumRecords AFTER INSERT under tableX to accumulate the records
inserted by hour
if there is an error in the commands executed for this record, <record1> is
not in the tableX

If this occurs in a trigger BEFORE INSERT, I can understand, but, if it is
AFTER INSERT, I believe that the record is already inserted.
What is wrong on it?

Thanks in advance
Josi Perez