Search optimization is generally beneficial for ensuring that content is discoverable through search. However, it is possible to go too far and over-optimize, according to Google. Harmful over-optimization involves optimizing to the point where it becomes spammy, which can result in a decrease in rank or no ranking at all. Two examples of harmful over-optimization tactics are keyword stuffing, which involves excessively repeating keywords to rank higher, and building links with exact-match anchor text, which can indicate the manipulation of links. On the other hand, time-wasting over-optimization occurs when efforts in optimization have diminishing returns. Examples of this include obsessing over small details that only have minimal impact or spending excessive time fixing redirect chains and optimizing every meta description and title tag. It is important to prioritize optimization efforts and focus on areas that will have the greatest benefit to search visibility. If actions feel like they may be disliked by Google or users, or if there is excessive fixation on minor improvements in already performing areas, it is likely that over-optimization is occurring.

source: How to Avoid Search Over-Optimization