"The most important thing I took away from my work experience" + "was that a great teacher is compassionate" or "is that a great teacher is compassionate"?
Which tense is correct? Present because I still have the thing I took away or past because I took it away from a past event?
What you took and the time you took it is besides the point. Your concern is between the tense of the main clause and the tense of the final clause, the verb tense in the adjective clause “(that) I took away from my work experience” is irrelevant.
Main clause:
The most important thing was/is
Dependent:
that a great teacher is compassionate
You want to show same time action between the main and dependent:
CORRECT: "The most important thing I took away from my work experience is that a great teacher is compassionate.”
The fact “is” is the verb for the teacher, makes it a fact that the teacher was and is and probably will always be a compassionate teacher. The verb “is” is Present Tense used to state facts or show habitual action.
“thing” is / teacher is compassionate [thing = fact AND teacher compassionate = fact]
If you really want to get grammatical, I'll show you that not only is the verb "is" Present Tense but also that it is a linking verb that links the subject to the noun or adjective on the other side of the verb, and in your sentence, that would be the noun clause "that a great teacher is compassionate" which serves the purpose of being a noun in the sentence, known as the predicate nominative."
I have sources to prove everything I am saying to you.
EDIT:
You can leave out the modifier. After all it is only acting as an adjective. The final clause is essential BY THE RULES OF how a linking verb performs in a sentence.
"The most important thing is that a great teacher is compassionate."
BTW, if you did use "was" that means an action started and ended before now, and that would mean the compassion of the teacher ENDED at some time in the past.
"The most important thing is that a great teacher was compassionate."
Our language is very complicated, you come to one realization after another as you work with the rules and discover your mistakes along the way. Mine is rushing to get this typed.
SECOND EDIT:
The reason I make a big issue out of the "linking verb" is that the noun clause as a predicate nominative, a noun, "identifies" or "explains" the subject, and the subject is "thing." "thing" is a pronoun that has as its antecedent (the word the pronoun refers to ) the noun clause on the other side of the linking verb.
You said, the most important thing is... Is thing "what you walked away with" or by the rules of grammar...is thing the noun on the other side of the linking verb. It is. The most important thing is not what you walk away with but the fact the teacher is compassionate. I'm done. Thanks for reading this.
Use "is".
The most important thing I took away from my work experience is/was being on time.
"Being", or whatever verb you would use in the example, is in the present participle form, so the preceding verb should be in the present tense.
Edit: "Was" is the correct word. Non-finite verbs ("being", etc.) do not affect the the tense of the rest of the sentence. So, "was" should be used and match the (past) tense of "took".
One should use was:
"The most important thing I took away from my work experience was (not is) that a great teacher is compassionate."
... because I took it away from my work experience in the past.
If I were giving a speech on what I learned from a work experience I was just completing, I might say:
"The most important thing I'm taking away from my work experience is (not was) that a great teacher is compassionate."
Addendum: Based on the exchange below with @deadrat, I suggest the following:
If you still believe that "a great teacher is compassionate" -- for you that is an enduring truth -- you should use is:
"The most important thing I took away from my work experience is that a great teacher is compassionate."
If you no longer believe that "a great teacher is compassionate" -- for you that is not an enduring truth -- you should use was:
"The most important thing I took away from my work experience was that a great teacher is compassionate."
May we abbreviate to “The thing I took from my experience was/is a lesson”?
This can be about truth or endurance only if altering the thing taken necessarily alters the grammar. A single answer must cover piles of money or souvenir ashtrays as well as enduring truth.
Rather, this is like migration, although I lack the vocabulary to name the parts.
Migrants either way; whether we immigrated here, or emigrated from there, depends on which end of the journey we’re considering. The price of the ticket and whether the ship sank change nothing.
My family lived in Ireland for hundreds of years but in the end, we emigrated to the USA… once we got there, life was wonderful
My family has lived in the USA for a hundred years but in the beginning, we immigrated from Ireland… once we got here, life was wonderful
Whether it was ten minutes or a century ago, when this trinket is from Ruritania, the origin of the thing is more important than its nature as a trinket. This is true whether or not the thing is still used as a trinket.
If this trinket was from Ruritania, the nature of the thing as a trinket is more important than its origin in Ruritania. This will remain true if, say, the “trinket” was a piece of silk cut from a traditional Ruritanian garment to be framed as a purely decorative tapestry, with no connection to Ruritania visible to anyone except the most adept of the cognoscenti.
