General Struggle:
* Strive: To make a great effort to achieve something.
* Contend: To struggle or compete.
* Wrestle: To struggle physically or mentally.
* Grapple: To struggle to cope with something difficult.
* Battle: To fight or struggle against something difficult.
Internal Struggle:
* Conflict: A disagreement or argument.
* Agony: Extreme physical or mental suffering.
* Torment: Severe mental or physical suffering.
* Anguish: Severe mental suffering.
* Dismay: Loss of courage or hope.
External Struggle:
* Hardship: A difficult or unpleasant situation.
* Adversity: A difficult or unfavorable situation.
* Trial: A difficult or testing experience.
* Challenge: A difficult task or situation.
* Obstacle: Something that prevents progress.
More specific words:
* Agitation: A state of anxiety or nervousness.
* Toil: To work hard and long.
* Labor: To work hard, especially physically.
* Contention: A heated disagreement.
* Friction: A disagreement or conflict.
The best word to use will depend on the specific context.