If you are a new parent, you might be fooled into thinking that every little thing that you do for your kid must be perfect. Just the right amount of music played softly at night...eating only the best foods...breastfeeding...applying in a spot for preschool years in advance...homeschooling!
What if I do the wrong thing and my kid becomes an axe murderer? What if they never go to Harvard? What if I let them cry too long and they are psychologically damaged? Don't the experts agree that everything must be just right, that I am ruining my child if I don't follow their advice exactly?
"Modern psychology says..." insert non-sense here. Modern psychology (or really "pop psychology" in book or blog form) is responsible for all the whimpering, cowardly, self-centered brats that are walking around in sports coats and high heels with the bodies of middle-aged men and women and the emotional and intellectual state of a 12 year old. I wouldn't put much stock in what they say.
Trust me, I have 5 kids and we have tried different things with all of them, different sleep methods, feeding methods, eating habits, etc. They are all equally psychologically damaged.
You are not ruining your child. THE KID IS ALREADY RUINED! The moment that little tyke was conceived in the womb of his mother he was already a screwed-up sinner. There is nothing you can do to ensure that he will be the perfect offspring. You already cursed him with the same curse that your parents gave to you, a corrupt nature.
So if you want to feel guilt, feel guilt because you are a sinner and you have passed it along to your kids.
BUT, and it is a big BUT, this is why Christ has come. To paraphrase Saint Paul, "In Christ Jesus neither the Cry-It-Out method, nor the Respond-Right-Now method count for anything, but a New Creation!" Jesus makes sinners into saints with His blood, His Word, His Gospel.
In Christ you are forgiven for being the screw-up of a parent that you are. In Christ your child is forgiven for being the selfish brat that we all were at one time. In Christ even the pop psychologists are forgiven for placing their pompous guilt trips on everyone.
Love your child. Do what you can to keep them safe from real, present day threats. Show them that you love them, even if it means discipline. Laugh with them. Cry with them. And if you mess up, repent. Lay it all at the foot of the cross, and let Jesus Christ make you, and your children, His new creation.