Dear Mauvega
Do not panic. Steps are simple. You need to do FBRA. For each step, where there is a subsequent clearing to be reset, system gives message in the status bar saying "Document XXXX YYYYYYYYY is not purely a clearing document" (Where X denotes company code and Y denotes a document number).
Just double click the message and read it. It gives you the information about the dependent document that need to be reversed first. See below;
Follow the steps till you reach the last document to be reversed.
Hope this make your understanding better?
Regards