I've been practicing meditation since the beginning of the year & just recently started meditating 2 hours a day & listening to TMI audiobook for some guidance until my knowledge of all the various practices and theory begins to expand.

I believe I'm at the 3rd stage, with some mind wandering, occasionally; however, I've run into an issue that the book doesn't seem to touch on. When I'm meditating for long periods like I have been doing (1h sits), I tend to get very strong dreamlike mental imagery. Moreover, I find it quite difficult to distinguish between this mental imagery and my actual senses as time goes on. Either my focus and/or energy depletes, or it even feels that the mental imagery is intertwined with my senses (I can't pinpoint the exact cause).

What should I do in this situation, do you think?

Well, what's the actual problem? Why do you think strong imagery is wrong?

Are you getting sleepy? It's normal to have intense mental imagery (and other types of sensations) as you approach sleep. It's called the hypnogogic state. It is also sometimes hard for people to tell the difference between hypnogogic hallucinations (imagery / sounds / etc) and reality. 

​​​​​​​Even if you are not feeling sleepy, you can enter this state if you are very relaxed.

If it is hypnogogia, the way to handle it would depend on your particular situation. One thing to do is to just observe it. Or treat it like any other mind wandering. Or get some sleep. Or change your technique so you don't get so deeply relaxed.  If you are meditating lying down, try meditating sitting up.

A lot of mental turbulence is due to stress and mental fatigue, so I find preparing for meditation by relaxing can result in better mindfulness if I relax first and then come up out of the deeply relaxed state and then being to practice vipassana.

Sleepiness is the most likely candidate, I think. And yes, it is somewhat difficult to tell the difference between the hypngogic imagery & reality. In fact, almost like synaesthesia, the images have some sort of correspondence or generate some sort of representation of that which I'm trying to observe. For example, you might be paying attention to the expanding of your belly & there is an image in your mind of some animated figure becoming larger & then smaller, with the breath.

So, somehow I can follow the breath to a limited degree, whilst almost in parallel, noticing the imagery. However, the imagery can distract me, or I let the imagery take over as representation of the breath rather than perceiving the breath more directly, which can lead to reductions in the detail and accuracy of the following of the breath. That last sentence is a bit of a mouthful, sorry.
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Sometimes I solve problems using abstract 'structures' that map onto the structure of the problem more or less directly, like an analogy, but I 'feel'/'perceive' the structure as some sort of - not necessarily visual - image; more in the realm of a higher-dimensional image schema. It's not something I always use in my thought processes, but the correspondence between the breath and the hypnagogic imagery has some resemblance, intuitively, at least. 


Honestly, however, I think it may be because of an excessive effort during my meditation. Not longer after I posted, I meditated for 45min (was going to do an hour, but something came up), but stayed on stage 2. I think I might still be at stage 2, but at times it helps to still ask myself, "what am I focusing on?" or, "am I distracted?", or simply go out about that general intention. Somehow, my meditation session felt more productive.

At the same time, yesterday, for the first 40min of my meditation in the morning, I applied introspective or metacognitive introspective awareness (I need to look into the distinction some more, as I haven't gone far into reading about stage 4 yet) quite intensely & with high motivation. I was very frequently revisiting what my primary focus was & then moving away from distractions and toward my breath, noticing sensations in a much higher level of detail than normal. I felt what Ni Nurta has described as unrefined 4th Jhana, where the shape of my body feels as if it has partly dissolved & has become a much larger & voluminous shape - like the sensations of the skin of my stomach are inside what I 'sense' or think to be the boundaries of my stomach. I hope this is enough detail, but I can push for more if it would help your analysis.


Thanks very much for your help

There's nothing to overcome. Inquire into it. Become interested in it. It is a part of your experience. There are no boundaries of what is right or wrong in your experience. It's just another thing to explore. Isn't it interesting how these thoughts seem to have substance? How they seem to erase a boundary between your "waking state" and dream state? Is there a boundary between these states? How much of your waking experience is real or imagined? Where do these hypnogic mental images end and your waking thoughts begin? This is such a fun thing to explore! Take it as an opportunity. Your whole life is an opportunity to explore and inquire.