Sade Sati is a 7.5 years of Saturn transit that get triggered when Saturn comes 12th from your birth moon sign. If you were born with a Gemini moon at birth, then later down the line, when Saturn's yearly transits comes 12th house from your moon signs, all the way to 2nd house from your moon sign is known as Sade Sati. Saturn stays in one signs for 2.5 years, so when Saturn is 12th from the moon, with the moon then 2nd house from the moon; these 3 house transit is about 7.5 years.
Why is Sade Sati known as a period of hardship in your horoscope, trails & tribulations? This is because Saturn is a teacher like Jupiter, but Saturn is a bit harsher than Jupiter. Saturn loves to show your reality of your life and present to you in 'Now', where Jupiter gives optimism about the future. Saturn is not a bad guy, Saturn is actually the planet you want in your life. Too much time do we spent in day dreaming and fantasizing about the future or thinking about the past. Saturn wants you to live in now, he wants you to face your current surroundings. Like Ekhart Tolle said "You are not your mind, and you are not your thoughts. You are , NOW".
What Sade Sati does come, it re-polishes you as a person and turns you into gold towards the end. Even though most people lose a family member during this time or face lots of accidents, this is because of your past life karmas. How good or bad are your past life karmas were, will show how good or bad your Sade Sati will be in this life. The past life is judge through the placement of Saturn, Rahu and Ketu, including your 'Moon Sign Chart'. I say this because not everyone has a hard time in Sade Sati, some excel to new heights, depending upon how well placed their moon is.
What are the remedies though for Sade Sati? The one remedy i will tell you to avoid is wearing the iron ring in your middle finger. This will do more harm than good as it will trigger Saturn. You are playing with 4.5 billion year old energy that wants to teach you a lesson for your own benefit, but here you are, trying to avoid it with a stupid ring. Stay away from gemstones and these type or remedies, they will cost you more than the return.
What does work is you pouring 2 litter milk on a Shivling in a temple. Just two litter or below, as per 'Nirmal Baba'. Since Saturn is controlled by Shiva, you appeasing Shiva, will make Saturn go easy on you. You can do this one Saturday a month during twilight time. Also, if you or any of your family members ever killed a snake, then you must, must do this because killing a snake triggers life long struggle since snake is the ride of Shiva.