what could jesus possibly mean that we have to strive? whats the word in the greek?

good question. it means to strain every nerve as in a fight to the death. from this greek root we get our english word agonize.

Cognate: 75 agōnízomai (from 73 /agṓn, "conflict/struggle," the root of the English term, "agonize") – properly, to struggle, like engaged in an intense athletic contest or warfare (Souter). See 73 (agōn).

https://www.merriam-webster.com/dictionary/agonize

Definition of agonize
agonized; agonizing
transitive verb
: to cause to suffer agony : torture
intransitive verb
1 : to suffer agony, torture, or anguish

agonizes over every decision

2 : struggle

at the very least it looks like he was saying to put some effort into it.


http://biblehub.com/greek/75.htm

agónizomai: to contend for a prize, struggle
Original Word: ἀγωνίζομαι
Part of Speech: Verb
Transliteration: agónizomai
Phonetic Spelling: (ag-o-nid'-zom-ahee)
Short Definition: I strive, contend
Definition: I am struggling, striving (as in an athletic contest or warfare); I contend, as with an adversary.

Thayer's Greek Lexicon
STRONGS NT 75: ἀγωνίζομαι

ἀγωνίζομαι; imperfect ἠγωνιζόμην; perfect ἠγώνισμαι; a deponent middle verb (cf. Winer's Grammar, 260 (244)); (ἀγών);

1. to enter a contest; contend in the gymnastic games: 1 Corinthians 9:25.

2. universally, to contend with adversaries, fight: followed by ἵνα μή, John 18:36.

3. figuratively to contend, struggle, with difficulties and dangers antagonistic to the gospel: Colossians 1:29; 1 Timothy 4:10 (L T Tr text WH text; for Rec. ὀνειδιζόμεθα); ἀγωνίζομαι ἀγῶνα (often used by the Greeks also, especially the Attic), 1 Timothy 6:12; 2 Timothy 4:7.

4. to endeavor with strenuous zeal, strife, to obtain something; followed by an infinitive, Luke 13:24; ὑπέρ τίνος ἐν ταῖς προσευχαῖς, ἵνα, Colossians 4:12. (Compare: ἀνταγωνίζομαι, ἐπαγωνίζομαι, καταγωνίζομαι, συναγωνίζομαι.)

Strong's Exhaustive Concordance
fight, labor fervently, strive.

From agon; to struggle, literally (to compete for a prize), figuratively (to contend with an adversary), or genitive case (to endeavor to accomplish something) -- fight, labor fervently, strive.

and last thing, its a verb. a verb is an action, not a thought process. not an acquirement of knowledge. not a mental exercise. not some thing you can do very well sitting on your butt.

By faith Moses, when he was come to years, refused to be called the son of Pharaoh’s daughter; choosing rather to suffer affliction with the people of God, than to enjoy the pleasures of sin for a season; esteeming the reproach of Christ greater riches than the treasures in Egypt: for he had respect unto the recompence of the reward. HEBREWS 11:24-26

Wommack, Andrew. Discover the Keys to Staying Full of God (p. 57). Harrison House LLC. Kindle Edition.