It can be very, very hard to be honest. 

What helps is defining terms. To be factual is to be specific with all the facts and details. To be honest is to share true feelings and emotions, while sharing most of the details.  You can be honest without disclosing all the specific details. This can avoid conflict and protect relationships.

You don’t want to promise the reader that you are going to be completely honest or factual. That is a very high bar. Promising this is not being honest. 

Besides, a completely factual account of events makes for poor reading. A completely open and honest disclosure of all emotions can degrade to a poor reading as well. It could very well end up being a pity party or a true confessions novel.

The best reading is a combination of selected facts and honest feelings. People love stories. Never let the truth get in the way of good story.