Yoast snippet preview issue

I have installed the yoast plugin and tried to install the featured keyword to make it go bold in the Google snippet preview. Problem is that every word that is in the title or description is bolded, not just the keyword phrase I wanted to highlight.

For example the keyphrase I want to bold is: get him back forever. the title is ‘Learn how to get him back forever and keep him for life’. Problem is not only is ‘get him back forever’ bolded, however so is the word ‘him’ further in the title.

How do I change this so that only the words in sequence I wanted bolded are featured?

Thanks

Will