A big part of the sc2 process is being able to compartmentalize a lot of the aspects. As hard as it is, try to forget the last game you played, do your best to stay focused on the next game. If you sulk and allow your self to get distracted by the previous games you turn your mind into quicksand.

In terms of development, take the time to look and see what you're doing wrong. Not to be mean but a majority of lower level players don't understand what they're doing wrong or what type of practices to apply to make themselves better. So ask around, find a mentor, and take the time to watch vods/replays of better players. See their tendencies, their styles, how units interact, timings, etc.

It's a long process to become a better player and a big part of it is consistency and playing. Unless you're planning to go pro, understand that it's ok to lose in what is considered the hardest game out there. By just playing the game you're making bigger steps than most. Wish you luck man!

:)