Of course I can not say this will work for everyone but it does for me. Some people are motivated by getting on the scale, I do not. I like to see and feel my body change - by trying on those "skinny" jeans. It's my best measure. I have been working my but off for 1.5 years and I have not dropped a SINGLE pound! BUT I have dropped 3 pant sizes - that is an accomplishment.
Back to motivation during a workout - look at your waterbottle. The ounces on the side of the waterbottle is usually in the same increments of women's pant sizes. I just keep looking at that next number...I can do it!
Men - I am not sure how to help you, most men I have talked to do not need more than a quick look in the mirror with your shirt off.
Good luck, stay focused and find activities and food that work for you.