Put the verbs into the Past Perfect or Past Simple.
My friend said he (1-be) busy all day. He could not come to us before as he was packing his things. He was leaving the next day and everything had to be ready. When he (2-finish) packing, he suddenly (3-remember) that he (4-forget) to put his toothbrush in. Then he (5-unpack) the bag and (6-find) that he (7-pack) in not his toothbrush but his mother’s. He (8-laugh) at his mistake and (9-correct) it. When everything (10-be) ready, he suddenly (11-see) his belt, which was hanging on the back of the chair. He (12-forget) to pack it, too. Now he (13-become) frightened that he (14-leave) something he needed. So he (15-sit down) and (16-make) a list of the things he (17-pack) for the trip. He (18-understand) that he (19-leave) nothing else.