Some days, workouts are simply more challenging than others. You don't feel motivated or inspired. You blame your ennui on too little sleep, lack of hydration, and so on. While these variances might be part of the issue, there's a larger problem at hand - you're exercising with too many goals and not enough intention.
We talk a lot about intentions here at BuDhaGirl - they apply to our products, but they are also essential to leading a mindful life. Intentions make everything more focused and purposeful. When you put on your All Weather Bangles in the morning, you set intentions for your day, so why not set a few for your health and your workouts?
Keep in mind that exercise intentions shouldn't necessarily be goal-based. Instead of intending to run three miles because that's the next training goal on your schedule, take a moment to be present and self-aware. Take stock of how you feel, what you could benefit from, then set intentions for your workout accordingly. Challenge yourself to set intentions that aren't based on time, distance, calories or competition. When you release the idea of exercise results as quantifiable, your workout suddenly becomes expansive, exciting - a world of opportunity.
Set an intention to feel joy, to have fun, to practice self-love. There's no wrong answer and no limit. What's more motivating than that? Choose what you would like to gain from your exercise and for your health, then go... be it.