Giving them away to someone that will take their life quickly and with gratefulness for the food they provide is undoubtedly better than letting them fight to the death in a crowded space. Maybe that'll give you some reassurance.
The way I see it... nothing is immortal. They're all going to die. We're all going to die. You are not rendering them exempt from death by not making the specific choice to do the deed. Time as a set length that one has to reach to have a good life is a human construct. I believe that if chickens had language and a choice, they would much rather have a good one than a long one. Honestly, we should have the same mindset. I plan on doing away with myself before I am stuck in a nursing home turning to dust.
I set the eggs that gave rise to these birds, I let them have the chance at life rather than eating them as eggs. That choice I made also means I will have extra birds that don't fit into my coop or maybe make the other birds stressed due to hormonal behaviours. I give them a good life full of free ranging and yummy bugs. I treat them kindly, respectfully, and when it's their time, I kill them quickly and calmly and put their lives to a continuation of my own. I "could" sell them, but I don't trust random Craigslist people to take care of them with the same duty that I will. I see too many bare and muddy runs and pecked feathers around here. When I hatch or buy birds, it's taking on a contract to care for that bird in its best interest and kill it swiftly if it's hurting or if it's just best for the flock as a whole. In the wild, these things would be done by wild animals, which is much slower and more terrifying to the bird than a quick twist to the neck is done by me, a person they are comfortable around.
Dying of old age, something that sure wasn't a problem for the wild birds, is brutal. I fail to see the dignity that some ascribe to it. It's a fade so slow that you don't notice until one day you don't know where the animal or person you once knew is anymore. There are exceptions, and one can certainly age gracefully. But that's far from a constant.
I didn't always think this way. Some people never manage to come to peace with this mindset and would be happier with pets instead of livestock. I would say that yes, it gets easier... for most people. I know a person that is never going to process her own meat, despite growing up on a farm and being well acquainted with death and life. Take your time, come to your own conclusions, and do not continue in what you are doing if it only makes you miserable. Birds are a hobby for most of us on here, and having fun is good.
I have pet birds too... and I keep them as long as I possibly can. I put them down when they are suffering, and I am sad about it. I even cried over a few. Some may say "Well, what makes them more worthy of life than the meat birds?" The answer is nothing. It's purely human emotion picking favourites. That's not necessarily a bad thing, as I see it. Humans are weird by nature. We all have preferences that aren't explainable by hard logic. We don't need to cut all of that out, within reason anyway. That's what makes us human.
I've been in your position before. Years ago, I sold my favourite cockerel for meat because he was aggressive and I didn't know how to fix him. I felt sick afterwards. I liked him. But keeping him would have been dangerous to others and even myself, if he managed to get a hit in when I wasn't paying attention. I don't know if you'll find any of my ramblings helpful... just know you aren't alone here. I hope you can find something that works for you.
