I have been there. Several times. Just a month or so ago was the last time.
But today is my 7-month anniversary of sticking with it, and I feel proud of that. If I had given in to the lack of motivation and tiredness, I would be right back where I started 7 months ago.
Maybe you just need a little break. Continue your workouts but maybe do only half the amount of time you normally do. Or eat a couple hundred calories more per day next week. I find that when I am super tired, doing half of my regular exercise routine on one day per week helps me feel less tired. Don't give up, just maybe have one week (just one!) where you enjoy your success by toning things down a bit.
Another thing that helps me is variety. When I am bored, I will challenge myself. For example, I will try to do a vegetarian-only week, which exposes me to different foods I have never tried. Or a low-carb week, where I allow myself to eat lean cuts of beef while still watching my calorie intake. I will also change up my exercise routine and try a different cardio machine, or do cross-training on two or three machines during one workout. Variety helps keep me interested.
Good luck, and please don't give up. You will get through the dark days.