Am 23.01.2020 um 15:32 schrieb SuStel:

*jIQuch rIntaH.
*/I was happy (but that happiness is over forever)./

Are you sure? How can you deliberately decide to have completed being
happy?

Maybe you decide to live a happy life. When your life is over, your happiness is over, and you accomplished it.

Or maybe you decide to have happiness on the job. When you leave that job, that particular happiness is over, and you accomplished it.

In addition, if possible at all, it would mean that I have turned
to being happy, and that would last for ever.

That would be jIQuchchoH rIntaH. The addition of choH changes a quality verb into an action verb, and so follows what I said earlier about action verbs and rIntaH.

What does {jIQuchta'} mean?

TKD:
This suffix is similar to {-pu',} but it is used when an activity was
deliberately undertaken, the implication being that someone set out to
do something and in fact did it.

[...] instead of using the suffix {-ta',} [...] The resulting
construction, {rIntaH,} literally means "it continues to be finished" or
"it remains accomplished," It is used to indicate that the action
denoted by the preceding verb is a fait accompli: it is done, and it
cannot be undone.

My happiness is done and cannot be undone. It doesn't mean I am still happy or that my happiness is permanent; it just means that the happiness I experienced once upon a time cannot be undone.

-- 
SuStel
http://trimboli.name