Mind relaxation can be achieved by free imagination, without much arguing, memorizing or picking (when our will intrudes into our fantasies and dictates to us what to fantasize about). Loosening up one's mind requires having light, flexible, casual thoughts without focusing on any.
Imagination is useful in temporarily neutral unbiased thinking, to absorb maximum concepts without giving immediate opinion on any, e.g. relating to others' beliefs, lifestyles, perspectives, etc., without siding with any, until you make your final judgment. We should act like imaginative children, not stiff-headed adults, in the beginning of everything we don't know much about (as we all did in the beginning of life as children).
Imagination should precede an argument, since one cannot argue logically about something they can't sense, feel or relate to. Imagination is superior to memorizing and inferior to arguing. Understanding is best achieved in this order: imagine, argue then memorize.
Visualization is to imagine a possible future scenario, intentionally, in detail. It is mostly needed while one is relaxed to imagine that which makes one stressed. By doing so, one minimizes stress in advance before it attacks them. It is a voluntary detachment from the present, or a mind trip where you get out of yourself, temporarily, then look back at "you" from outside, thinking of you as somebody else, and of your problems as somebody else's.
Thinking in advance of stress, duties and responsibility you have towards yourself or others, makes doing your job easier and facing mishaps less surprising. It is especially needed when you must do a job you dislike or are not ready for, having to work, toil, move, talk, and think, simultaneously, multitasking and juggling many balls in the air without rest. Imagining an action before it's taken makes the energy it consumes well-calculated, with both success and failure less surprising.
Sometimes we have to consider all the possibilities of a situation, preparing ourselves for the worst even if it doesn't necessarily happen. When we know our role to play then, we move on and do other things, without waiting in suspense or feeding negative fantasies aroused by fears we can't control or reason with. Imagining worst-case scenarios is not pessimism; it is a form of visualization that leads to less pain and more pleasure, when done rationally—like a puzzle game we want to solve using most of our skills, without tension, and just for pleasure. (Schopenhauer's pessimism is good when used in the right context, leading to gratitude rather than discontent.)
Verbal repetition such as a mantra can be used for relaxation, focus or diversion. It can be short or long, meaningful or meaningless. We can repeat mantras or read them. Although they have a preliminary role in actual thinking, their role in self-control and physical balance is vital.
3. Slow Thinking
Slowness and relaxation go together. In fact, relaxation is to slow down with pleasure, whether physical slowness or mental slowness, i.e. slow thinking.