[MrRoboSteve]

A good mental model for programming the robot is that, each time your code executes, you should be answering the question "what should the robot be doing right now."

Consider the situation where you want to drive forward for a certain time. Each time the loop would execute, you'd ask the question "what should the robot be doing now.". In this case, you'd be examining your timer and saying something like this:

float elapsedtime = ...;
float timeToDriveForward = ...;
if (elapsedtime < timeToDriveForward)
{
// set motors to drive forward
}
else
{
// turn motors off
}

Note that each time this executes, you are either setting the motors to drive forward, or turning them off.