What is the word or term used to describe doing an activity or work with a high level of concentration and intention, trying your best? [closed]

Solution 1:

diligent

adj. Marked by persevering, painstaking effort.

diligence

Earnest and persistent application to an undertaking; steady effort; assiduity.

The Free Dictionary

Final tasks that had been neglected for months, and in some cases years, were being done with diligence under Jenny's eyes

Google Books

Solution 2:

You can say that you're performing the activity with focus:

focus, n.: the act of concentrating on a particular goal and not wasting time or energy on other things

Solution 3:

Meticulous

Meticulous - showing great attention to detail; very careful and precise.

Scrupulous

Scrupulous - diligent, thorough, and extremely attentive to details.

Solution 4:

assiduous

Defined by the American Heritage® Dictionary¹ as quoted by The Free Dictionary:

Showing or characterized by persistent attention or untiring application: an assiduous worker who strove for perfection; did assiduous research before writing the book.

^{1 _{American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.}}