You haven't been playing for very long. From my own beginnings, I've found that I inevitably hit a speed barrier. I can manage a piece quite well at a slower pace, but as I gradually increase the tempo, I reach a point where I cannot go any faster. Trying to push beyond this limit, I start making mistakes and lose a lot of the musicality. When this happens, I have to significantly reduce the tempo to correctly play the piece again.
What I've learned to do in these situations is to accept my final tempo, at least for the time being, and move on to the next piece.
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... feeling like the pianist on the Titanic ...