How can I use the verb "sad" in the past continuous? E.g.:
I was crying.
I was missing.
What should be the sentences for sad or upset in past continuous? Why do some words like the two above not follow standards? Are these exceptions?
Sad is an adjective, so it doesn't have a past form. You'd just say:
There is the verb sadden, however.
Upset can be a verb, but it's an irregular one. Its simple past (and past participle) form is upset.
Note that both sadden and upset are transitive verbs. (The intransitive usage of sadden is archaic.) So if you are going for past continuous, simply saying
wouldn't really work — it would raise the question, whom were you upsetting/saddening? So instead, you would have to say
There is no verb "sad" in English. It's an adjective. The closest you can get is "feel sad", which you can put in the past continuous:
Similarly, you can write
Cry and miss are two verbs; that is the reason you can say "I was crying" or "I was missing."