That part of the film devastated me when it came out, but it doesn't now because I know it doesn't have to be like that.
Life doesn't have to be a 'little bit worse' at all. It can actually be an opportunity for life to become 'a whole lot better' as long as you know your own worth and don't let someone else's actions define you or how your life will become.
Many years ago my husband had a brief affair quite similar to the one in the film, after we'd been married for 20+ years. The affair transformed us both. After the initial devastation, I decided that the most positive thing to do was to make this a catalyst for a better life - not a worse one - and that the only person who could make that happen in my own life was me.
My husband was on the same page and so he set about a transformation process on himself and faced his demons, taking complete responsibility for his behaviour. He realised very early on that the affair itself was fairly insignificant. It was just another example of his tendency to be selfish. He's a much better husband and indeed man than he was before. Staying with my husband was one of the wisest choices I've ever made but I only made it once I'd seen how life could be with someone who was an equal partner in our relationship, making the same efforts as me.
It kick-started my own transformation process too. Although I'd always been an assertive person at work and in relationships I'd formed as an adult, it made me realise I'd been making too many allowances for other people's bad behaviour towards me, specifically my family of origin.
The most powerful lesson I learnt was that I had a choice whether to surround myself with people who enhanced my life and that if I kept tolerating unacceptable behaviour, I had only myself to blame because that was a choice I'd made.
I'm a much happier woman all these years later. I've got a very happy marriage, amazing kids, a career I love, wonderful friends and renewed respect from my birth family.
The post-scripts I like to imagine for that film have different marriage outcomes but the same in terms of Emma Thompson's happiness.
One is that Alan Rickman realises how much he's been taking his wife and family for granted and makes changes, while she realises how much she's been defined by being a wife, mum and the PM's sister and starts realising her own individual potential. They stay together and they are much happier as individuals and as a couple. The other is that he doesn't change and she decides to go on the same individual journey to happiness and fulfilment as a person in her own right.
Life might get 'a little bit worse' or even 'a lot worse' if you let yourself become a victim of life and other people's behaviour. It gets a lot better once you decide that what ever your life becomes, it will be your choice.