Just do lighter weights and go through the motions. Is it you're mind or your body that doesn't want to work out? If it's that your too sore than cut back cause you're doing too much. Lower the weight, workout less, lower the intensity. You wanna have consistently ok workouts not 1 or 2 great work outs a week. Bodywise maybe your sleep isn't good or eat something before the gym instead of taking a pre workout. I like toast with peanut butter or oatmeal.
If it's your mind then try to listen to music that pumps you up. Set a goal for that workout that will make you feel like you won. Try to challenge yourself. See if you can do 12 reps instead of 10. Go up 5lbs on a lift. Sometimes some bicep curls just make me feel good.
If you're really struggling with exercise try to take up a physical hobby. Groupon has a lot of good deals on 1-3 month trials for stuff like kickboxing, boxing, bjj, indoor rock climbing, and I'm sure a lot of other stuff for cheap.
Yeah it's going to take a long time to hit your goal but that time was going to pass anyway. Instead of living the life you imagine, times gonna pass you by and you're going to get more
