I am kind of experiencing this myself, except ironically my life is not necessarily going well - I have just developed a better attitude/coping skills about it. I have battled PTSD and severe depression for the past 2 yrs. Therapy/group work/inner work and meds have finally seemed to kick in and I am actually feeling better. I am now apparently the 'happiest' person in my support group. I do not feel guilty for feeling good or worry about upsetting others. I am hopeful for them. If I could crawl out of the pit then I have faith that they can lift themselves up as well. I hope they can look at me and realize that it can get better. I'm no shining beacon or even a "success story" - I was down and now I'm up and I'll take it!
I remember when I was stressed about being unemployed, I sometimes got tired of hearing my friend talk about her job, especially if she was complaining. I felt resentful that she was griping about her job when I didn't even have one. But that was my problem and coming from a petty and bitter place in my mind. Now that I'm more optimistic (though still unemployed), I wouldn't care if she talks about her job. I guess my point is, you can control what you say, but you can't control how other people feel about it (or themselves) and react to it.
There is a difference between bragging about good fortune and simply acknowledging/celebrating it with people you care about. When I talk about my own joy, I am also wishing that joy on my friends and family - "I'm happy and I hope you are too. If you are struggling, I empathize and wish you comfort and success." I am reaching out instead of wallowing in my own misery. If others are not doing so well, I may or may not be able to commiserate by sharing my own story of woe, but I can still sympathize. I can still listen.
As long as your own happiness and good fortune don't prevent you from caring about those less happy or fortunate that you, you should not apologize or worry about sharing with them.
Joy should be inspirational and contagious - not a cause of jealousy or sadness!