A one line change is easier to review than a 1,000 line change.
Break down large changes into smaller logical units. Feature flags are helpful in introducing incremental changes.
Bug fixes and code refactors should be made separately from feature work; they’re easier to review in isolation.
Reviewing a 1,000 line change is tiring and time consuming. Smaller changes get more timely and detailed feedback because they’re easier to review.
Update 2021-10-26, a similiar sentiment is described in this “Small CLs” document from Google.