As someone who’s both been at uni a lot and taught at uni a little:
Your big advantage as a mature student is you know how to do a day’s work (I assume). Don’t be tempted to let up on that, it’s an advantage so use it. You’ll probably find you can sit down and get stuff done, be more organised etc. The above 9-5 suggestion is a good one.
A “disadvantage” is that you’ll probably care more about the course, and getting the most out of it. You’ve chosen to do this, rather than just fallen into it. Lectures are actually really hard work (I find) if you actually “care” about the content, and learning it, rather than just “getting it done” – you feel you have to pay attention more! My tip here (might not work for you, different strokes etc..) is before each lecture if you can skim the topics covered, note down a handful of things you expect to find out/get answers to in the lecture. As you get into the course this might include things you missed previously and think are important. Then at the end if you don’t get the answers, ask the questions or follow up with a quick chat with the lecturer at the end. A good way I found to stay focused and be sure you’re staying on top of things.
Also if you’re nervous, this is a concrete thing you can do to act on it, remove some of the nerves by knowing you’re taking useful action!