^^ I agree with that as well.
This is a complex question, because humans are complex creatures. The effects of psychedelics can be almost anything because they are mediated by an individual's brain, metabolic factors, state of mind, and (very importantly) the setting in which you take them. I'm curious as to what setting you took the LSD 2 years ago in? In your original post, you stated the intention to take mushrooms out in nature, which I think is a good idea, if you choose to go through with this.
Ultimately I don't think that one nightmare trip means you shouldn't ever trip again, especially since you say that since then you've gotten to the best place in life you've ever been. But care must be taken. If you do it, I would certainly say that you should not smoke any cannabis, and I would certainly say you should do it with a trusted friend, either with them doing it too or with them as a sober sitter. In case something goes wrong, I would never recommend being alone for a first trip (I realize you had one before but it was a disaster, so I'd say you haven't had a "successful" trip).
I don't think there's any harm in going into an experience framing it as a dialogue, but do remember that the dialogue is going to be between you and yourself. Terence was an interesting dude, but a little crazy in my opinion. Psychedelics are an internal, personal experience. The submission of the ego can be quite frightening, but sometimes it isn't too... my first trip was on mushrooms and I experienced oneness without any fear, and it changed my life. You will always do well to remember that you've taken a drug and whatever is happening will pass.
Do you have an anxiety disorder? I ask because you mentioned cannabis usually gives you anxiety. Just wondering, as that would make it riskier to trip. Cannabis for me does produce an awful lot of anxiety compared to almost any other drug, I'm good with it on its own but I often don't smoke on psychedelics until after the peak because it can make them so much stronger and more prone to anxiety.