You have exhausted every other option with your aging parent. Keep them in their own home and stop by regularly to help with meds, food, upkeep of the home, shopping. For a while that may work and you feel good about helping your parent and giving back when they have given so much to you during your lifetime.
As time progresses, your parents may find themselves unable to care for themselves on a daily basis. It is difficult for them to accomplish tasks and you may come to the point where you cannot trust their judgment. What if they leave the stove on? Or, wander outside and not know where they live. Worse yet, they get behind the wheel of their car when they are unable to drive responsibly.
We do not know what the future holds. It is impossible to promise your parent things like “we will never put you in a nursing home”, when we have no idea what situations will arise as they age with regard to their health and physical capabilities. It is hard not to feel guilty when you have run out of in-home care options. At this point, a tough decision may be in order. You have done the best you can and tried to honor their request. Because of modern medical advances, people live longer now than they did in the past. There comes a point in time when both their mental and physical capabilities may have deteriorated so much they cannot take care of themselves.