I go through those periods quite a bit, in fact I am going through one right now.
It's difficult to pull yourself out of it, at least I know that it is for me.
I don't have any friends to talk to and I deal with it by myself as best as possible. Time and maturity has also helped me deal with it better.

I don't tell my Master, I don't want him to know that I can be weak and not in control.
I don't even know what he could do though to help, just knowing he is there makes me feel good. If he tried to help out, it just wouldn't work, he can do all he can to keep my spirits up, and I try to get him to give me daily routine tasks and that helps out for me.
For me it's not just the fact that someone can tell me I mean something and I am important, or try to lift up my spirits. It's inevitably up to me to change my thinking habits.
It's hard to do though because once you get into that mindset, it takes a bit of work to move on from it.

I have OCD so I use CBT to change my thinking. I know that everyone is different so what works for me, may not work for another, but CBT does work for everyone. You can even incorporate it into a daily routine without making it seem like a huge change.

Here are some of the things that I do to get a better control over my thoughts.
I exercise, (not enough) but I try to get out and get some fresh air by walking, swimming, kyaking.
Eating right and at the right times, keeps me in check.
I keep busy by cleaning and rearranging my apartment.

When I feel particularly low, I write out my thoughts, why I feel this way, what is making me feel this way and the reasons I shouldn't feel this way.
I systematically work through my thoughts by writing them out and finding ways to feel a bit better.

Surprisingly, colour helps me quite a bit. By buying a few items that are bright and colourful, cheers me up.
Having bright flowers placed around the apartment, cheers me up as well.
I don't know why, but having something bright to look at makes me feel better.