This is actually a reply I posted to another thread a while ago in relation to transitioning and whether it was worse losing significant others to do so...but I feel it is a sentiment that pertains to your question as well.
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This is a question I ask myself every...single...day

I am currently going through my transition, I am 3 months on hormones and have recently lost my partner of 10 years...
She was and still is absolutely the woman of my dreams, and if I could do anything to change this situation that we have found ourselves in I would.
But the fact of the matter is, it simply couldn't work. I could never live a lie once I found out about my condition, and neither could she change her sexuality. So we had to part.
I am still very much going through the mourning process of an amazing relationship and a beautiful future lost...so I'm possibly not the best person to ask right now I guess :S
...
But I will say one thing that keeps me going through these times.
All that matters, all that determines whether transitioning was worth it or not...is how you deal with your loss.
No matter what it is you lose, Wife, children, family, friends, it's how you move on from your loss, and what you do with your life after, that determines whether losing it was worth it or not.
If you lose everything and give up...it will not feel worth it in the slightest.
But if you can lose everything, transition successfully, find a new partner that is more accepting, or replace whatever it is you lost, even if it is different, and manage to live a full and happy life?...Then it will certainly feel more than worth it when you look back.
...
It just won't feel worth it while you are going through it

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So in relation to your question? I would say that the grass can be greener, but only if you put in the effort to make it so.

Hope that helps ^^;