Try reminding yourself that you just took the steps necessary to ensure that your father will be living in a place where he'll be safe and comfortable, and able to get the care and attention he needs 24/7. Keep in mind that as his disease progresses, your father's needs will increase: Eventually he will need help with feeding and toileting, bathing and dressing. As his "internal clock" shifts (a common problem in Alzheimer's patients), he may need people who can be up with him at odd hours.
If he becomes aggressive or starts to wander, he'll need a secure environment with staff trained to deal with these behaviors. Unless you're blessed with unlimited resources and help, you probably can't meet his needs at home fully and safely.
Though you may feel guilty (who wouldn't in this situation), you really did the unselfish thing by determining what he needed, instead of what would have made you feel better. You're going to continue to be part of his world, so stop beating yourself up for not being able to be all things to your father. Try to move the focus from your feelings of guilt to thinking about how you and he can enjoy the time you have together in his new setting.
Dr. Mary A. Languirand, PhD is a clinical psychologist who co-authored "When Someone You Love Needs Nursing Home, Assisted Living, or In-Home Care." Read her full biography