Congrats on your solo! Having a student solo for the first time is one of the most satisfying parts of being an instructor.
The good part...you have your first solo done and behind you. The fear of being in the airplane(if there ever was any fear) should be almost gone. With that fear almost gone, it's easier to concentrate on the next phase of training.
The bad part...now comes the dreaded (but very necessary) cross-country work. A lot of work goes into cross-country planning, and for most people it's not as fun as training for your first solo. Pilotage vs. Dead-Reckoning, learning how to work an E6-B, fuel management, more communication procedures, more weather planning, etc. In my experience as an instructor, most of my students did not like the "cross-country phase" of training, mostly because it's not as exciting as just learning how to fly the airplane. But, once it's over and your Private license is in your hand, it's well worth the hard work. The first time you take a friend on a cross-country trip will feel great.
So, to answer your question about whether it gets any harder, to me the answer is not really. Rather than using the word "harder", I would use the words "not as exciting". Just keep looking to the day when that license is in your pocket!