I'm new to this forum so I don't know wether this is the right place to ask this or not, but I think it is so I'll go ahead.
After I got myself familiar with the popular classical piano repertoire, I became more interested in composing. Mostly in the late classical style (late Haydn, early/middle Beethoven, etc.). This happened about two years ago. After having composed several pieces in simple A-B-A forms I wanted to go on to some larger scaled works like full scale sonata works.
However, I got stuck right at the beginning. Whilst simple themes would do just perfectly for the simple pieces I composed before, they simple didn't sit right with me and so I went on analyzing how Beethoven's and Haydn's themes were constructed. What I noticed was that both of them created themes out of sometimes just one motif. I also noticed that this happened more in Beethoven's music than Haydn's. Nevertheless, it also looks like the themes for his earlier compositions are mostly constructed from rhythmic idea, and then those beats where filled in with chord tones of the particular key.
So, I followed this example. Composed several themes every day, but still, none of them were good enough for me, and I couldn't develop a lot out of them. So, I ask you fellow composers and brilliant minds (I hope): How to write themes like Haydn and Beethoven did? Is there any way how we can now?
Thanks in advance!