Whittle away
Definition 1 of 2
Pro Tip 1/3Gradual Decline
Emphasizes something being reduced little by little, often subtly. 
The old park's beauty was whittled away by neglect.
Pro Tip 2/3Silent Erosion
Indicates the erosion of something in a way that's not immediately noticeable. 
Years of harsh weather whittled away the statue's intricate details.
Pro Tip 3/3Negative Impact
Used when the reduction of something is undesirable or harmful. 
Incessant criticism whittled away her self-esteem.