When forget, regret and remember are followed by a gerund, the gerund refers to an action that happened earlier than the main verb. The gerund could be replaced by the present perfect participle in these sentences to make the sequence of events more explicit. Forget is frequently used with never in the simple future form.
- I remember locking the door. = I remember having locked the door.
- He regretted speaking so rudely. = He regretted having spoken so rudely.
- I don't remember losing my glasses. = I don't remember having lost my glasses.
- I will never forget meeting my boss for the first time.
When these verbs are followed by a infinitive, the infinitive refers to an action happening at the same time of the main verb, or later.
- This morning I remembered to lock the door. (= the remembering came first, then the locking)
- Do not forget to buy some eggs. (= the not forgetting comes first, then the buying eggs)
- I forgot to bring my books to school. (= first I forgot, then I didn't bring my books.)
- We regret to announce the late arrival of the 12.45 from Paddington. (= our regrets come before the announcement)