Dr. Barbara Fredrickson, author of the book Positivity: Groundbreaking Research to Release Your Inner Optimist and Thrive provides an online and free lab-tested tool to assess an individual's positive emotions versus negative emotions. According to her research a 3-to-1 positive ratio leads people to the tipping point where they become resilient to any adversity and effortlessly achieve their dreams/private thoughts/musings.
A coachee who does not achieve such a high and healthy ratio has a lot of scope for seeing things differently, if they acquire the right skillsets and knowledge - with support from the coach and others of course. This tool can be quite emotionally challenging for people, so use it wisely, only with those who can cope well enough beforehand as you might not the right person to help take them from where they are now, to where they should be...a lot of the negativity might be outside work context, and if it is in the work context, you certainly have a lot of work to do.
Again this is a scaling test, so mood and environment are big - HUGE - influences on the results.
Quiet space and 5 minutes
Provide Barbara's Positivity Test to the coachee. I suggest doing the assessment at the beginning of the day, before work really begins.
Discuss the results with the coachee. If the coachee wants to improve their positivity ratio, keeping an effective diary, other tools available on Barbara's website, and books like Stephen R Covey's The 7 Habits of Highly Effective People are good places to start, as well as of course whatever tools you as coach already have. You can once again set some goals and assist creating a coaching plan to achieve them!