If I've done something that's made me feel a bit silly and useless (not saying you are, just with low self esteem it's something I go through a lot!), my first step is always thinking about things rationally! Just sitting down and going through the facts of a situation, on paper or mentally, helps me see things in a less "clouded" way - stops me getting caught up in blame, guilt, etc - and then allows me to get on with improving my low mood.

Things that help me the most next are taking a really nice long bath - doing something that's "for me" just makes me feel the love for myself again! Also listening to my favourite upbeat music whilst doing chores helps me shake off the blues, it's a great mix of emotional and psychical positivity! In the long term I'll then focus on things I have to look forward to, or have accomplished, no matter how small. If I was having a really bad day, I'd likely do all of the above and it usually sorts my mood out.