The Third Principle of Self-love is that love for yourself alone is only right and nothing else is possible and nothing else can cause you to be happy.
Egoism is the doctrine that I should be selfish in a way that harms none intentionally. Egotism is the doctrine that I should be selfish and harm others if I want to. Altruism is the doctrine that I should not love myself but just love other people. Altruism is one and the same thing as sacrifice and declares that love is sacrifice. You have to believe in and follow one of these. You cannot move from one to the other and you have to stick with one. It would be inconsistent to egoistically make a grand meal for yourself and say you believe in altruism too while an altruist would prepare the meal for a friend. Because you cannot be happy if you do not use your head carefully for reason is in you for your self-preservation, the strongest instinct you possess, logic says choose egoism. It is best for you and for others.
When I sacrifice, I nevertheless do what I want to do under the circumstances so it is not a sacrifice for I am after gratification. When I say I want a car it is not the car that is important to me but the desire for the car and I have the desire for one end, self-gratification. Anything I do, I feel I want to do. Even when I hate doing it I feel it is best to do it under the circumstances so I like it more than I hate it. This is a very comforting thought. Be aware that when you are doing something that makes you feel bad that you want to do it more than not to and focus on this fact. This makes you feel happier about it. It makes you feel free and cherish that feeling. It helps you get over it.
I cannot help loving only myself and nobody else. When I say I love somebody I only mean I like what they do for me and enjoy my feelings and thoughts for them. I do not value them. I value myself because it is my delights I value. Therefore altruism is not an option.
The new fashion expressed in the view that doing good for others because you enjoy it and want to help them is unselfish is seriously mistaken. If you want to be unselfish, or altruistic as it is sometimes called, you have to believe that you should do nothing for yourself but just do it all for others and that the more you suffer to help others the better and if you should suffer so much then you should walk ten miles to get somebody a glass of milk if they ask you. Why? Because if helping others because it gives you emotional fulfilment is unselfishness then looking for money for yourself has got to be unselfishness as well for the motive or goal is the same: gratification. It is only the focus of your desires that is different and it is the motive that counts in determining if an action is selfish or unselfish. Unselfishness, thankfully, is impossible though there are disordered forms of selfishness that are disguised as unselfishness.
Those who tell you that you must sacrifice yourself and be altruistic or to love God or others are destructive to your self-esteem for they are telling you that you are only good if you can do the impossible.