Keyword optimization is a great way to get high search engine rankings and a better online presence. However, the misuse of keywords just to increase keyword density is not a good practice. It provides a negative user experience and diversely affects search engine rankings.
Place the keywords distinctively throughout the website content so that it looks natural to read. Never stuff keywords in the title tag, heading or page content. Use only those keywords which you feel are relevant to your content and have value to a visitor.