its not always hellish, but when you first start it can be. it is different for everyone
If you try to draw a line from a single point, it can lead anywhere. Do not assume that your single experience is the same as everyones. You are likely to encounter some disturbing images as you learn to focus and control your dreams. This is normal, as the sleeping mind is even harder to control than the conscious mind. Keep trying, keep practicing. Not all your experiences will be bad. It’s very much like life. What you put into it is what you’ll get out of it.
Lucid dreaming is a very difficult topic. Obviously our dreams are separate from reality- they are controlled by our subconscious and thus so are difficult to control. We need our dreams to expel any negative thoughts/emotions that are conscious doesn’t want to deal with.
In trying to control lucid dreaming, you are trying to ignore the things which the subconscious wants to explore so to start with they are going to be random, sporadic and sometimes even difficult because you are trying to control something that is relatively uncontrollable.
Like people have said- each experience is different, but you need to be careful. Our dreams exist to help us battle things that we cannot/or do not want to face in daily life….. so if you do have a Hellish experience just remember that it is normal.