Title self explanatory - Monroe was definitely experienced in astral exploration. If anyone was going to be prepared I think he would have been,

But how do we know if he really did 100%

From this website- https://www.insightstate.com/spirituality/robert-monroe-quotes/

Below are 18 Robert Monroe quotes about the out of body experience (OBE):

#1 “Advanced souls know that they cannot change the system and they don’t wish to. They are content to enjoy themselves in the Earth Life System and the only influence they exert is to maximize their experience.”

#2 “The supermind knows unquestionably what is “right,” and problems result only when the conscious mind stubbornly refuses to recognize this superior knowledge.”

#3 ”The most difficult mental process of all is to consider objectively any concept which, if accepted as fact, will toss into discard a lifetime of training and experience.”

#4 ”Fear is the great barrier to human growth.”

#5 “Honesty is the best policy because there can be nothing less.”

#6 ”Emotion is the key to and the driving force underlying every thought and action in human existence.”

#7 “The greatest illusion is that mankind has limitations.”

#8 ”I am more than my physical body. Because I am more than physical matter, I can perceive that which is greater than the physical world.”

#9 ”Exercise your Human Mind as full as possible, knowing it is only an exercise.”

#10 “Always know and remember that you are more than your physical body.”

#11 ”There is no beginning. There is no end. There is only change.”

#12 ”The only way you can obtain [love] is through shared life experience, and even then there is no guarantee. The deeper, more intense the shared experience, the less time it takes.”

#13 ”The major reasons for attending the human experience school are first, to learn to translate the original Prime Energy into discernible form and second, to become a first-order generator of the original Prime Energy.”

#14 “The depth of learning is in direct relation to the intensity of the experience.”

#15 ”Don’t get addicted to being human. This is only temporary.”

#16 “For those who would die, there is life. For those who would dream, there is reality. For those who would hope, there is knowledge. For those who would grow, there is eternity.”

#17 ”Consciousness is a thing that inhabits a physical body, driven and controlled by the mind. There is a very valid purpose to why it is that way.”

#18 ”I looked down at the bed, and there was my wife in bed, and there was someone in bed with her. I thought in an amused way, “Whom would I dream to be in bed with my wife?”