Guilt About Euthanasia

I feel so much guilt. My cat Squeaky was old ( 17 + years) and so skinny. She would eat sometimes and would love her food then the next day hate it. I tried so many kinds of cat food, boiled chicken etc. She was vomiting and I was trying to give her pills, but it was so hard to get her to swallow the pills and I felt I was hurting her.. Finally, she seemed to have began to lose control of her back legs. I thought it was time. But now I regret not waiting a few days