If you are in the habit of doing divination, you will find that there are times where reading is difficult at best. You will also find that there are times where you really are not in the proper headspace for divination. Being in the wrong mental state for a divination session can, at times, lead to results that are heavily skewed in one direction or the other. It can also lead to results that are essentially pure gibberish. A quick glance through the different pages on the internet discussing divination of pretty much any form will show that many who provide information on techniques and tools strongly encourage the people following their methods to avoid readings at 'bad' times. Unfortunately, it is difficult to determine what exactly a 'bad' time to do readings would be.
Thus, I wish to present a partial list that is both the fruit of experience and what I was taught when I was just beginning to dip a toe into divination. Before I go much farther, I wish to make a note that everyone's tolerances for stressors and distractions are different. Things that would put me into a place where I simply don't have the focus necessary for a divination session to be productive may be a non-issue for someone else. Alternatively, there will be scenarios that I can perform a divination session with very few problems but will render another reader too distressed to proceed.
1. Do not read while upset or in an agitated mindset.
This may sound like a no brainer. Performing a divination session when you are in a mental state where there is a great deal of anxiety, sorrow, and overwhelmed distress front loads your mind to seek out the results that would confirm these impressions. In a state of high anger, you will find that results that confirm and encourage your anger are easier to pick up on than those that would deny that powerful emotion. This is not because these results are more potent as much as you are so focused on that pattern in your experience, you will spot similar patterns in your environment. Much like happening to see more blue cars because you are focusing on blue vehicles, though the actually percentage of blue cars on the road has not changed.
2. Do not read while incapacitated due to intoxication.
I don't have any problems with someone enjoying their entheogen of choice. When used properly, they can actually contribute to the accuracy and depth of a reading. This said, discretion is necessary when performing a reading under the influence. When the entheogen saturation is such that one has difficulties with distinguishing between fantasy and reality, this is a poor time to do a reading because it will be difficult to winnow out the accurate results from the false. If the reader's mental state is such that they can not clearly discern between the results of the reading, the results that their personal bias promote (which usually do not align completely with the genuine results of the reading), and the random side-effects of the entheogen that they have consumed, they would be best off setting aside the divination session until they are more clear headed.
3. Do not read while incapacitated due to illness.
Now this bullet point has a few provisos to consider. If the reader is regularly in a state that most would consider incapacitated due to illness and is intimately familiar with what the body of information their senses give them during this state, this should only be applicable when the reader is literally not well enough to perform divination or dealing with symptomology that falls outside of their usual operating norms. Secondly, what can lay one person low and render them too ill to perform divination will be different from another person. The one who should be making the judgment call as to if the divination session should be happening is the person who is performing the divination. They know their own limitations best. The only time that this should be challenged is if the literal act of divination puts them into a position where their health and welfare is compromised.
Performing divination while sick can be done. It is, however, more difficult because the information that the body gives us while we are unwell is going to be a distraction from the information we are seeking in our divination session. The effects of our illness may mimic those of intoxication, or the effects of our medications will do the same. In some cases, illness will encourage the person's entrance into a receptive mental state for psychic experiences. This, however, is not the usual course of affairs with illness. If one suspects this is the case, a vigorous test of the psychic experiences as they unfurl to ascertain the legitimacy of the results is highly advisable.
4. Do not read while heavily invested in a specific outcome.
This is, in many ways, much the same as what I mentioned in point one. Approaching a divination session and seeking out a specific result makes the chances of having a false positive indicating the desired result much higher. In cases where the practitioner can not read with out a strong position on what outcome should be presented, the divination session should be postponed until the reader has a greater sense of detachment from the query. Failing this, a confirmation divination session with a different practitioner is highly advisable. This second session will serve to help detach the outcome bias of the initial reader from the results of that first session. I personally will seek out a third divination session with another individual that has no interest in the result of the session as a surety against the results being swayed.