You're not a disappointment, in fact, I bet you're the complete opposite. But feeling these feelings are very common, unfortunately.
Whenever I feel this way (and trust me, I do a lot) I usually clean up my room, go take a walk outside while listening to music, you know that sort of thing. My most favorite thing to do however, is to draw. Drawing is an effective and creative way to forget about negative thoughts you feel throughout everyday life. But, that's just my opinion.
Basically, doing what makes you happy lets you forget about these feelings of sorrow....hope this helps ^^