Hi Pooch
I completely agree with all the comments about the issues being situational and hopefully transient, rather than this being an inherent part of YOU which you need to change or "fix". And others have made some really good suggestions (I second the one of St John's Wort, btw) far more eloquently than I.
What I would say re ridding your life of people who drag you down (Lizbeth always refers to such people as "being a drain, not a radiator") is that it is a helpful thing to do in so many ways; not only does it remove that negativity from your life but it can also feel as you are taking action, taking charge, doing something. And for planners like us ... that's helpful.
I've posted before about a "friend" (you may recall ...) with whom I always had huge issues around money whenever we went out - she would go to any lengths to not pay and would be very passive aggressive about it - much sighing, counting out the cash veeery slowly, disputing the bill, constantly saying she was broke*, lots more. Not only did it wind me up at the time, but I'd fret about it happening before I saw her and I came to dread having time with her in any environment where Paying For Something was on the agenda.
After a while, I just told myself that this was idiocy and that life was (is) too short to spend it dreading time with such a person. So I just sent her a reply to her latest moaning missive, acknowledging it and the points she made ("oh dear, poor you, I agree that having lots of filing to do at work is awful, but at least you have your forthcoming trip to Australia to look forward to ..." *) and then said at the end: "I will be out of touch for a while now - I have some issues, both personal and professional to work through and I need a bit of space to do that. I'll be in touch again when I can."
[* not actually broke at all, as we can see ...]
She replied saying "Fair enough, thanks for letting me know", then carried on her email in the usual style; I ignored that note with a clear conscience and that was that.
I feel far freer and lighter not having her in my life and I'm glad I've done it, in what I hope was a reasonably gentle way. So, just to say - it can be done and it's worth it.
Hope things improve for you soon. Hugs to H & H - and you 
Cleo x