Question State and Action

From what I understand, する is used to express action, and している is used to express state but in some situations or contexts how do you consider if in any given context a verb should be expressed as a state (i.e. express in している・していた form) or an action (i.e. express in する・した form). I'm having a hard time differentiating action from the state. Some types of verb (especially verb that is related to the mind) is really close to being a state for example, 怒った and 怒っていた

この金額はどう見ても（足りない・足りてない）じゃん。

2年（付き合った・付き合っていた）彼女と別れた。(This one quite confuse me, I thought it'd be 付き合っていた but I found out that 付き合った is being used in the same context as well)

Hi @NoWayYesWay, I'm not a native speaker, but here are my thoughts:

The plain dictionary form of a verb like する is used to express an action that will be performed, or is performed regularly:
明日勉強をする I will study tomorrow, or
週末にはテレビを見る I watch TV on the weekends

The 〜ている form is used to express a state of doing the verb being conjugated, AKA the present progressive form:
I am watching TV so please be quiet テレビを見ているから静かにしてください, or
It seems like they still don't understand the reason they got dumped まだ振られた理由が分かっていないようだ。

Of course, they can also both be nominalized and used in different ways to form more complex sentences. We usually run into trouble when we're trying to express a specific grammatical nuance that may bleed over from our native language.

For your examples:
足りる is a bit of a different case because it's not a verb that describes an action with a direct object, it actually describes a state itself (of being "enough," or sufficient). Both of your examples sound fine to me, but 足りない sounds more like a general statement, whereas 足りていない seems more like it's "not enough for the current need."

Similarly, 付き合う also describes the state of going with/dating someone. I think as an English speaker I also tend to overuse the present progressive in cases like this, because in English we might say "the girl I was dating for two years broke up with me." But in Japanese it is unnecessary; you dated for two years, what point is there to make it present tense, especially when it is now over and your sentence ends in the simple past tense?

Sorry for the late reply.

Thank you @nice gaijin for your answer but please let me ask one more question.

One of the usages of ～ている is to express the action that someone has done (state of someone has already done something) for example;
・今まであんたの描いた絵を見せていたのは私だけだよね？
・先週あたりも誘ってくれていたが、夜が遅いので、泣く泣く断った。
・私はぎりぎりになるまで先延ばしにしていた。
・自衛隊によるインド洋での給油活動とイラクの復興支援活動に派遣された自衛隊員のうち５６人が、派遣後、在職中に自殺していたことが、．．．

In these examples (sorry but I do have a problem with ～ていた cases more) ～ていた expresses that the subject has already done with the action and was in that state at that time and I can't see any difference if I change ていた in these examples to just た; I mean these examples, with た form will simply express that the subject did something, with ていた form will express that the subject was in the state of already done something in the past (the moment that being referred to) which means the subject did something thus, in my opinion, they're the same so, what's the difference and how do you consider if at any given context ～ていた is preferred over ～た

I think its a very subtle difference. The difference is so subtle, you can confidently replace any of those ていた situations with a simple た, and the meaning of the sentences would be unchanged and grammatically correct.

Note I'm not a native speaker either.
Maybe there is a slight preference for the continuous state when narrating something. That last sentence certainly feels like た would be just as good (if not better) than ていた.

NoWayYesWay said:

Sorry for the late reply.

Thank you @nice gaijin for your answer but please let me ask one more question.

One of the usages of ～ている is to express the action that someone has done (state of someone has already done something) for example;
・今まであんたの描いた絵を見せていたのは私だけだよね？
・先週あたりも誘ってくれていたが、夜が遅いので、泣く泣く断った。
・私はぎりぎりになるまで先延ばしにしていた。
・自衛隊によるインド洋での給油活動とイラクの復興支援活動に派遣された自衛隊員のうち５６人が、派遣後、在職中に自殺していたことが、．．．

In these examples (sorry but I do have a problem with ～ていた cases more) ～ていた expresses that the subject has already done with the action and was in that state at that time and I can't see any difference if I change ていた in these examples to just た; I mean these examples, with た form will simply express that the subject did something, with ていた form will express that the subject was in the state of already done something in the past (the moment that being referred to) which means the subject did something thus, in my opinion, they're the same so, what's the difference and how do you consider if at any given context ～ていた is preferred over ～た

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No worries, it's a forum, there's no expectation for you to respond immediately. In fact, it's usually best when people spend a little more time crafting their posts than the average text message

Are these examples from a native source? Honestly I could see them using the plain form and being perfectly understandable.

It's hard to gauge whether this information is useful because your examples are rather complex, but one thing to be aware of is "state-change" verbs, where upon completion, the verb marks the change from one state to another. 結婚する、開く、閉める、死ぬ、and 自殺する for example, all express such a state change. So when you are using the 〜ている conjugation, it doesn't mean that the verbs are "in progress" as they normally do, but indicate that the verb is complete and the subject is in the changed state (is married, open, closed, dead, etc)

NoWayYesWay said:

・今まであんたの描いた絵を見せていたのは私だけだよね？

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To me this implies the art was shown a number of times over a period of time.

NoWayYesWay said:

・先週あたりも誘ってくれていたが、夜が遅いので、泣く泣く断った。

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To me this implies he/she invited him/her several times, not just once.

NoWayYesWay said:

・私はぎりぎりになるまで先延ばしにしていた。

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This feels the same to me either way.

NoWayYesWay said:

・自衛隊によるインド洋での給油活動とイラクの復興支援活動に派遣された自衛隊員のうち５６人が、派遣後、在職中に自殺していたことが、．．．

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This also feels like several suicides occurring over the course of some time.

I could be totally wrong since I'm not native either. Just my general sense.

The point is your examples are the past form, except the first one. Whether it's ～た or ～ていた, it expresses a perfect tense, i.e., the action is completed. That's why it seems to express a state in those sentences.