Sir, how to deal with suspicious thought once it settled in the mind and no way to know the real truth. It just takes away the every precious present moment of one's own life, which could have otherwise lived and enjoyed.
The only way is to surrender to a guru and gain the ultimate knowledge on what the mind is. You are absolutely correct that the mind is preventing us from living in the present. It is continuously commenting on the past and worried about the future.
To live life we do not need mind! This is very difficult to understand. Mind is like a cricket or football commentator. When the game is going on, AFTER the happening of a particular event, the commentator talks about it. If we watch the game in the stadium we do not need the commentator.
Similarly, if we live life each moment as it comes, there is no role for the mind. Mind merely assumes that it is the doer leading to suffering. Just as the commentator DOES NOT influence the play in ANYWAY, our mind also cannot influence our life in anyway. But our mind is ignorant of this fact.
As long as we are ignorant of this fact we are at the mercy of the mind. It will continue to trouble us. Only when we forget ourselves by getting involved in the action completely we are free of our mind. Only then we enjoy our natural joy.
This happens mostly when we are absorbed in a good book, music, movie or sports. It happens rarely in our day to day experience of life. For example when we fall in love, in the company of the lover we forget the world and immerse in our natural joy. But the mind soon wakes up and prevent us from continuously enjoying the present.
That is the nature of mind. Unless we gain this ultimate knowledge of mind, it is very difficult if not impossible to deal with suspicious thought.
Thanks for asking this important question. If you need more clarifications, please do ask.