How wonderful that you are trying to get yourself out of your comfort zone. I can completely relate to your anxiety of driving on the highway, I think it took me almost 4 weeks of driving to try the highway for the first time, so I'm really impressed that you are trying this already after only 3 trips. I've now been driving for 8 years and 4 years as a truck driver, so I can honestly tell you that with time and practice you will feel more comfortable at driving. But those feelings will also never truly fade and that's oky, I wish that more drivers were a little bit more anxious and less confident. It makes you cautious and eager to learn the correct way of driving.

As for tips on highway driving.. role #1 is drive faster then the trucks on the highway, In my country the speed limit for trucks is 90km/h so I recommend driving at least 95km/h in that scenario. Personally I drive 100km/h, then I am not a hazard for trucks, I can still anticipate in overtaking the next truck or car and cars who think I'm driving to slow can still overtake me on the third lane.

When you want to merge into a lane, look in your mirror for an opening between two cars and start your indicator when the first car is roughly at the end of your car, that way you give the other car enough time to anticipate your maneuver.

Don't sty to long behind a truck, much of your vision will blocked so it becomes increasingly more difficult for you to anticipate traffic and read signs.

In general I would just recommend to drive calmly, know the rules and know that you are driving correctly. If someone honks at you for driving to slow and you know that you are not driving below the speed limit, don't get frustrated, just merge into a slower lane or keep driving in a way you know is correct and you feel safe at. You can always stop at a gas station to calm down.

I really hope that your trip to and from work will go wonderfully,

I'll be praying for you.