You have done the impossible, but it just doesn’t feel that special because it is a thing of the past. You have grown since then. The person that found it ‘impossible’ no longer exists. Thus it is increasingly easy to discount those accomplishments.

Try to remember how hard it was, and despite that difficulty, you persisted and succeeded any way.

Realise that this will happen again. What you think of as impossible, will (with time and effort) be overcome, and it too will become easy.