The Two Second Rule
Here is the 'two second rule' which will help you keep the correct minimum distance from the car in front.
When the car in front passes a streetlight or other clear marker, start saying to yourself
"Only A fool breaks the two second rule."
If your car passes the same marker before you have finished the sentence then you are driving too close.
There is also an extended version of the two second rule to say to yourself in poor driving conditions:
"Only a fool breaks the two second rule; in cold rain and snow at least doubly so."
Effectively, you are reminding yourself that the standard two second rule only applies in optimum driving conditions. Once the weather closes in you must be at least twice the distance to ensure the safety of the drivers and passengers of both vehicles.