Broomstick Pilot....
Firstly, it is really good that you're going ahead with an ATPL course with the current climate in the industry. Unlike most others, I firmly believe that the market will pick up in the next couple of years. If this is the case there will be a strong demand for pilots with good training and sound aptitudes - especially since many major airlines have delayed or cancelled training courses of late. These airlines could find themselves with a considerable skills shortage if the market picks up more quickly than they predict.
To answer your question, having recently started my ATPL, I find the most taxing aspect of the course is the sheer volume of material to learn rather than the complexity of it. From this respect I totally agree with what has previously been said - get quickly into a routine of revising what you have learned that day - if you get behind it can be hard to catch up.
Try not to lose sight of your goals either. Despite the vast expense of the course, and the time and effort spent going through various selection process, there are times in ground school when people begin to lose motivation. This is a perfectly normal reaction - the courses are tough and intensive because they have to be. The upside being the rewards of successfully completing the course - these are very high (if, like me, your dream job is being a pilot!) and should remain foremost in your mind - that way you'll have no trouble....
I wish you all the best for your future.
DEXY