My head used to be a mess - ADHD, years ago. That's all in the past for me because I train, mentally, every day. As part of my business, I've taught and trained thousands of people online to resolve that type of issue, but there's nothing easy about doing so - simple, but not easy, because the brain simply will not go quietly into obedience.
The average mind is like a team of wild horses (thoughts, feelings, impulses & urges) strapped to a wagon (you). Every single horse wants to be in charge and yank the wagon around in one direction or another. The willful effort of reining them in to quiet them down and get them working in one unified direction is the most challenging, enlightening, and life-changing pursuit a human being can engage in, because doing so affects every single area of life - mental, physical, spiritual, financial, social, and personal relationships.
If you want to begin getting your mind to slow down - get your thoughts to be more organized, even develop the ability to set aside thought and enjoy moments of quiet inner peace even while in the midst of being productive, learn the skill to remember without having to constantly think, then simple mental exercises (well-practiced with an objective for mastery) will do the trick.
The techniques should be centered around "Attention Control" skills, and can be as practical as spending 30 to 45 minutes a day combining useful approaches such as sitting in a quiet place and pouring every ounce of your attention into experiencing every breath you take (fully, evenly, in and out) while dismissing and refusing to participate in any thought that arises on the stage of consciousness.
The second half of the mental training routine can be something like taking a candle and placing it about arm-length away at eye level or slightly above (psychological/neurological reasons for doing so) and investing every single bit of attention into the flame, refusing again to participate in any form of thought, self-talk, or external distraction, ensuring that the only thing that matters in the world is your visual and mental connection to the flame.
Eventually, you discover the nature of Attention - that it will obey your command; the nature of Thought, that the voice and pictures going on in your head only SEEM like you, but are merely conditioned, rambling reactions conditioned into your brain like a broken record; and you'll discover the truth that, since you are NOT your thoughts (literally and experiential), there's a different, higher way to go about daily life without their constant harassment.
