Like you I trained both TKD and Hapkido. I also found Hapkido much more challenging. Hapkido was more challenging because of the reasons you mentioned, and also it was tougher on my body in ways that I wasn't use to. I tried to train them together and found myself getting more frustrated. If I had just picked one and focused on that I would have done better. Which is what I eventually did.
I don't think any art has come naturally to me, but I do think some aspects of training are more challenging for me than others. I would assume that is normal.
You need to work on your acting.