There is a class of verbs in Persian which are stationary. That is to say, they govern an “action” in which there is no movement:

نشستن
nešastan
‘to sit’

خوابیدن
xābidan
‘to sleep, go to bed’

ایستادن
istādan
‘to stand’

The construction of the present progressive of these stationary verbs is derived from the participle. With the می prefix all of these verbs govern an action which is either in the process of taking place before becoming stationary, or is going to take place (as in the future tense). Compare the following sentences; also compare and contrast them with their English counterparts:

من اینجا می نشینم
man injā mi nešinam
“I am going to sit here.”

من دارم اینجا می نشینم
man dāram injā mi nešinam
“I am (in the process of) sitting (down) here.”

او اینجا نشسته است
u injā nešaste ast
“He/she is sitting here.”

او نشسته است تا من برسم
u nešaste ast tā man berasam
“He/she is sitting [there] (waiting for) me to arrive.” (literally, “until I arrive”)

اینجا می نشینی تا آن ها بیایند؟
injā mi nešini tā ān hā biyāyand?
“Are you going to sit here until they show up?” (literally, “come”)

من دو ساعت است (که) اینجا نشسته ام
man do sā’at ast (ke) injā nešaste am
“I have been sitting here for two hours.”

من اینجا می خوابم
man injā mi xābam
“I am going to sleep/lie down here.”

من دارم اینجا می خوابم
man dāram injā mi xābam
“I am (in the process of) sleeping (as in going to bed) here.”

من دارم می خوابم
man dāram mi xābam
“I am going to bed.”

من اینجا خوابیده ام
man injā xābide am
“I am sleeping/lying down here.”

من خوابیده ام
man injā xābide am
“I am sleeping/asleep.”

من تا صبح همینجا می خوابم
man tā sobh haminjā mi xābam
“I am going to sleep here until morning.”

من سه روز است اینجا خوابیده ام
man se ruz ast injā xābide am
“I have been sleeping here for three days.”

من اینجا می ایستم
man injā mi istam
“I am going to stand here.”

من دارم می ایستم
man dāram injā mi istam
“I am standing up.”

من اینجا ایستاده ام
man injā istāde am
“I am standing here.”

من تا صبح همینجا می ایستم
man tā sobh haminjā mi istam
“I am going to stand here until morning.”

من از صبح اینجا ایستاده ام
man az sobh injā istāde am
“I have been standing here since this morning.”

من اینجا می افتم
man injā mi oftam
“I am going to fall/crash here.”
(note semantic parallel between the word افتادن as ‘to crash’, both as slang in Persian and English)

من دارم اینجا می افتم
man dāram injā mi oftam
“I am (in the process of) falling/crashing here.”

من اینجا افتاده ام
man injā oftāde am
“I am lying down here.” (as in not moving)

من از صبح اینجا افتاده ام
man az sobh injā oftāde am
“I have been lying here since this morning, I have been lying down here since this morning.”

In the construction of the past progressive of these verbs, the present copulas are simply replaced with the past copulas:

من اینجا نشسته ام
man injā nešaste am
“I am sitting here.”

من آنجا نشسته بودم
man injā nešaste am
“I was sitting there.”

Note that من آنجا می نشستم man ānjā mi nešastam means “I used to sit there.”