Scarlett - by the time you get this, you will have got through Day 1 - hope you survived and that it went well.
I too remember the feelings of fear and dread at the prospect of returning to work after a period of long-term absence. However, as is the case with many things, the worrying about it can be far worse than doing it - I hope this was the case for you. I do remember that on my first day back, colleagues were genuinely pleased to see me and welcoming which made all the difference and really, I had worried unneccessarily
Also, events in the future always seem so far away and yet, when you look back, you can't believe how quickly time has passed - it's the middle of September already and it doesn't seem any time since Easter! It'll be Christmas before you know it!
You can and will get through these feelings - good luck!