I used to feel bad because I did not understand it.

The process of learning, from the stage of it being in a miasma to the stage of getting a grip on a subject, is one of those swirling whirlpools that can become enjoyable the more one does it. 

So today when I forgot how to say something in a language I haven't used for a while, I realised that  - I used to feel bad because I didn't understand it. Now I don't feel bad because I only forgot it.