Hi On The Edge,
Please try to replace your self-talk with something more positive:
"Today is very difficult for me."
More difficult than being without your family would be? Because it's a choice, and keeping everyone in your life is not one of the options.
"The sadness of the loss of the ow is consuming me again."
If you could be with the OW today, wouldn't you be miserable, missing your family and feeling guilty then too?
"I hate the fact that I'll be with extended family today because I won't be there in spirit."
That's really sad, because you are depriving yourself and your family of the joy of being together. Instead of dwelling on what's missing, why not focus on what do you have? I know this is hard but it's not impossible. I am a BS but we have a similar struggle: BS's have to deal with the loss of the WS during the affair but have to focus on the children left behind, making sure they don't feel neglected, helping them deal with the depression, and trying to make life for them seem as normal as possible. So I know it's very difficult... but not impossible.
"I have had moments of clarity & an hour later despair. I had clarity this morning until about noon & it's been agony since. Luckily the sermon at Mass spoke to me & gave some hope."
This is something that you will have to actively work at. There will be times when you just drift back and forth between clarity and the fog of the addiction, but you can also purposely expose yourself to whatever it takes to maintain the proper mindset. (Again, even though I am not a WS, we BS's have experienced the same thing with missing our WS's but having to accept that we can't have them while they are with OP)
Since the sermon helped you, then you could turn more to religion, for example.
"Thanks for listening. I'd appreciate any suggestions to help deal with the grief & fear."
Allow yourself to enjoy your wife and family. Hug your wife a lot. Look at her - enjoy her beauty and goodness. Have fun. You know how you smile because you feel good and frown because you're angry or sad? Well, it's been proven that it works the other way too. If you smile and act happy you WILL feel better.
"I have a very good wife which is great but adds to my guilt."
If you are not currently doing anything to feel guilty about - then don't. If you are doing something to feel guilty about (contacting OW, unfairly comparing OW to your wife, remembering the OW's good points but denying to yourself she had any faults, fantasizing about OW) then knock it off. I read somewhere that guilt is a fake emotion. You don't feel guilty unless you are aware of wrongdiong. Once yoacknowledge wrongdoign you have a choice to make - whether or not to continue. Choosing to continue but then pretending remorse is dishonest. I don't know if I completely agree with that philosophy...but it doesn't make sense to feel bad about doing something... IF you choose to do it anyway.
"There is every reason in the world I should stay in my marriage & not go to OW. But this is a matter of the heart..powerful s***."
No actually, it's not really even a matter of the heart. It's simple chemistry (how's that for an oxymoron - simple chemsitry). You are literally fighting a chemical addiction. It's just like you were taking mega doses of antidepressants so your seratonin level was sky high during the affair. Now you are being weaned off that chemical high down to a more normal state. (That's why you may need antidepressant prescription to help for a while - so you don't have to quit the chemical addiction cold turkey) When you've kicked the addiction you will be able to make decisions of the heart once again. Until then you are going to have to use the help of counseling, your wife who has stood by you, probably an antidepressant from your doctor, exercise, more of those sermons, and this message board to help you stay on the wagon.
The affair most likely would have ended whether or not your wife waited for you any longer. The chemistry always wars off in every realtionship. But unlike marriages based on real love and trust affairs rarely lead to a satisfying long-term relationship (only about 5%) and when that 'in love' feeling begins to fade, adultery partners know they can't count on each other to stick it out until the feelings reignite, right? Because affairs are based on selfishness, deception, and fantasy. It's tough to go through the withdrawal when you still feel 'in love' but the alternative would prove much more devastating in other ways. You're lucky you are getting clean now before more damage can be done to everyone involved, families ripped apart, and legal committments made between adultery partners (who would have to be temporarily insane to trust each other). You're lucky you have your wife and family to help you through withdrawal. Some people don't put a stop to the affair in time and lose everyone first and have nobody to help them when reality hits.
I don't know if I was much help. I probably sounded too much like I was giving you a lecture, too much like a BS...