need help with doom and gloom thoughts

I have fairly rapidly progressing disease that is not responding too well to chemo and I am on prednisone that makes me very emotional. Add these 2 together and it is not a mix for a happy outlook. I find myself dwelling on things like this is going to be my last Valentine's day ( more than likely true ) and each family milestone that passes reminds me that this is the last one. I realize this isn't helpful but I can't control it.
Any ideas on how to handle these negative thoughts. I understand the saying live for each day but as each day passes, it seems like there are fewer left.
Hope this isn't too much of a downer.

Today is Valentines day! I woke up to sun and a pancake breakfast cooked by my loving hubby!My daughter sent me gorgeous flowers! It is our 17thy anniversary in addition to V day. My son and his family are coming for a visit and pizza later today. I have stage IV ca -mets to brain- know from what all is going on my time is very limited. I do take a day at a time. God Bless everyone of them! Today iw beautiful. Tomorrow may not be but God willing I will be alive to enjoy whatever God hands me for the day. Please dont give up- Use whatever energy you have to focus positive and enjoy time with friends and family even if you just sit and talk. Sometimes I mowst pleasure just curled up in my favorite chair talking to my kids and watching the grandchildren play . God will watch over you and we are all in this together. You have many angels here and elsewhere watching over you. Stay strong. God Blesss. PattyD

Feeling "down" is natural at times like these. I Thinkback to the time 2 years ago that I was given less than a 50% chance to live out the year. What did I do??
First - I decided to surround myself with positive and restful energy, like playing the CD's that help me relax and get out of my self pity. I kept the answering machine ON so I don't have to get the phone if I didn't feel like talking to anyone. (Some people have a way of trying to help, but making you feel worse.)
Second - I decided to get rid of some stress by taking care of some nagging things that had been sitting around and staring me in the face. (With over a year of treatments and all, I was tired and letting some things pile up that I needed to take charge of.)
Third - a decision to try and be the "exceptional cancer patient" came over me when my mind and heart had cleared a little. I found the book "the Making of Herceptin." I read about people liker Ginger Empy (who I always wanted to somehow contact and let her know how her story had inspired me - and here she is on this site!)
Fourth - during the period of not knowing whether my tumors would respond to treatment, I tried to devote just a little time to what I would like for my final days and burial. I got something satisfactory in mind, but did not write it down, thinking I will do that when the time is nearer.
Well, I still havenot written those things down as I came out of my poor prospects with a much better than expected outcome.
Try to somehow take charge of your days - try to get something postive doneeach day and you WILL feel better.
Easier said than done - as I have been in those shoes. Took a great deal of effort to manage. Let yourself find strength in some activity, whether only mental. It will help.

Dear Steph N.
I just wanted to tell you: THANK YOU!!! Your answer was very helpfull. I do not want to writte anything else, but I could´nt go sleep without telling you how well your words did!