A "bad" practice can leave you feeling demoralized and unmotivated about your personal cultivation for weeks.
If we take a look into what characterizes a "bad" practice, and what characterizes a "good" practice, we can gain some deeper insight into what is really going on.
For many of us, if we sit down to meditate - for example - and all we can do is think the whole period, we may label this a "bad" practice.
Other times, we get on the yoga mat, and we are just not feeling as flexible, compassionate, or peaceful as we are "supposed" to when we do this practice.
The problem here is that we've allowed our practice to become infected with a "should".
What's the problem with a "should"? Well, a "should" is different than a goal. A goal is something like "I'd like to be able to hold the crane pose in yoga for five breaths in two months", or "I'd like to be able to concentrate my mind peacefully for 20 minutes straight by this time next year". These are reasonable, achievable milestones that one can aim one's practice toward.
Shoulds, on the other hand, are unreasonable in that they are usually saying that whatever is happening is not what is "supposed" to be happening. This "supposed" to does not help one get toward ones goals. In the Dao De Ching - an ancient Chinese classic, advises us "the journey of 1000 miles starts with the first step". When we are focusing on the shoulds, we are focusing on some other step than the one in front of us. This makes it practically impossible to get to our goals in the long run - and makes us feel bad about ourselves in the short run.
Anyone who has been able to take a practice and make it consistent - like skilled atheletes, or musicians - can tell you that you have to take the good days with the bad days. Now this isn't some pessimistic view that says "practice will always be hard" - there are many masters who have reached a place of lasting peace - it is just the knowledge that a bad day doesn't mean that something is wrong with your practice.
The bad days are, in fact, something very right with your practice. There is a phase of meditation that I like to call "beginners luck" - when you just get to sit quietly and "at peace". For most, this phase only lasts for about a week, until you get quiet enough to actually hear all that was going on under the surface level of your mind. These noisier practice days can, at times, be a good sign that you are actually getting more sensitive.
The same can be true if you are attempting to integrate a new level of ethics or integrity into your life. There may be many days as you being that you feel you are doing much worse, but it's actually just because you are finally paying attention.
Finally, the rough points in our daily cultivation form the raw material for our inner growth. It's an evolutionary practice - we have to struggle with it, we have to push ourselves in order to grow. It can't just be roses and rainbows all the time - that's just not realistic for most, and even if it was, it's not especially beneficial.
When working to make your practice stick - to make it a part of your life, learn to stick with it no matter what. It can be extremely exciting when we make some stride in our meditation, yoga, or anything else, but what we are really looking for is the type of patient mind that can continue on during a dry spell. If we are looking at the big picture, this type of patient and enduring mind is actually what we're attempting to develop through all of this meditation and yoga. The way we can develop it is through learning to simply be with our practice - whether it seems exciting at the moment, or a little dull. With this ability to stay, we will notice over time that our level does increase, our experience does qualitatively better, and our practice matures.
Action steps:
Find out what for you constitutes a "bad" practice. When you have this type of session, does it derail you?
What are the goals of your practices contrasted with the "shoulds"?
If you are not experiencing difficult practice days, do you think you are expanding or progressing in your personal cultivation?