I have a question about other practices that I’ve been told would be detrimental to continue while I pursue the path laid down by Yogananda. I am referring to Trance Channeling, Spiritualism, and Hypnosis. I am having a very hard time understanding why these subjects have been labeled as bad.
Good question, Travis. First of all, let me say that “spiritualism” is a tricky term: Depending on whom you’re talking with, it can mean anything from worshiping God to trying to connect with departed souls. I gather that your question refers to the latter, but I can’t be sure, so forgive me if I miss your point on that term.
One can indeed connect with disembodied spirits by “channeling” or “contacting the spirit world.” The question is, what kind of spirits are they? Are they highly advanced spiritually? Not necessarily; in fact, highly unlikely. Swami Kriyananda has often said, “The great masters simply don’t come that way. You have to lift yourself up to their level, rather than expecting them to come down to yours.” If you go away from home and leave your front door open, who’s most likely to walk in: an honest person, or someone who’s looking to steal from you? So on the subject of channeling, the question is, Whom do you want to come into your consciousness?
That is not to say that channeling is sure to result in an unhappy circumstance. Only to say that the results are uncertain, and in any case, it is not a way to lift your level of consciousness.
Rather than open the mind passively to whatever wants to come in, Yoganandaji taught meditation as a way lift the mind to the level where only those of high consciousness reside. Then you can commune with them, absorbing vibrations that you can be certain are beneficial for you.
This takes, among other things, tremendous willpower (though not a forcing kind of will). Willpower is absolutely crucial on the spiritual path. For this reason, Yoganandaji recommended against the sort of hypnosis in which one gives one’s will over to the influence someone else, because it weakens the will, which is so vital to connecting with God.
One final point: If you are pursuing a particular spiritual guru/path, it is best to lay aside all other practices. That is not to say that they are all “bad” by any means, but practicing what the guru has offered, and only what the guru has offered, is itself a way of tuning in to his or her vibration. If that is the path you have chosen, why linger on other paths, even "good" ones? Anything else has the potential to—in fact, likely will—dilute your own ability to tune in.