I am the world's biggest control freak, but I genuinely think demand feeding is the least stressful option.
In practice, for me at least ( I've bf 3 kids for blinking ages!) demand feeding doesn't mean no routine at all. Babies settle into their own little routine, and you can tweak it a bit to suit, so if I was going to the supermarket and wanted to try to get all the way round in one go, I would stick baby on in the car and encourage him to feed. Similarily, before I went to bed I would schedule in a good long sit on the sofa ( at least 45 minutes) and I would feed baby, swapping sides and back again, tickling his feet a bit to (gently) stop him dropping off, and then I would get a decent block of sleep at the start of the night. You get to know your baby, and you can plan accordingly.
I think you have to be realistic about what it will be like at first, and give your self a couple of weeks at the start when you know that feeding is your priority. If you go into it knowing that it will be like this, and you are aware that there will be times (particularily at 10 days and 6 weeks) when baby will be having a growth spurt and will feed ALOT, but this doesn't mean you don't have enough milk, it's really not stressful.
I found using a ring sling really helpful, because I could feed and look after the other kids etc. In fact, I don't remember baby number 3 ever really crying, because I just fed her whenever she made a noise...it was very stress free!
Sometimes babies just want a quick drink, they are after fore-milk, not hind-milk, so it will feel like they are hungry all the time, but they are just thirsty! Also, some babies feed quickly and some slowly, so you can't really judge what a full feed is. They stop when they are ready, and you can encourage them back on but you have to trust that they know what they are doing!
IME, women who go on to bf exclusively for any length of time bf on demand, and trust in the ability of their body to feed the baby it produced!
Good luck with it all 