I just started a new job, and everything's been great... except for one thing. I have one very difficult coworker. I just cannot seem to get along with this person and I find myself feeling upset just thinking about interacting with him. Do you have any advice for dealing with difficult coworkers?

For as long as I can remember, I've been told, "you're just lazy," "you're scatterbrained," or "get your act together." These types of negative messages have had a deep impact on me after all these years. Now that there's so much awareness around ADHD, I've been wondering if it's time to find out if there are some underlying causes for my problems that have been overlooked. Where do I start? 

I know I could be better at my job, but I am hesitant to ask for what I need to be successful at work because I don’t want my boss to think any less of me. How can I speak up for myself better?