Sad to be weaning - any advice?

I'm thinking about weaning baby off bf. He already has one bottle of formula a day as I work part time. With seven sharp teeth, latching is very 'ouch' and he only seems to feed now for about two minutes. But he's my last baby and I feel SO SAD about the idea. I'll miss that close time in the morning and night especially!

How do you know when it's the right time to give up; and
What do you do to overcome the sadness and not feel guilty or have regrets after the fact?

I'm so scared I'll look back in twelve months time and regret giving up, and I'll never get the experience or time back in the same way.

Any advice?