Appreciation is such a challenge. We have so many options that are more appealing than appreciating or accepting appreciation. We could envy others or be mad at them for succeeding. We can dismiss it instead of receiving it. We can - and many times do - walk in darker paths than the ones we want to walk on.
I heard that if it's easier for you to appreciate other people, like your friends or employees, you could imagine that you were your own employee. How would you appreciate that employee for the work they're doing? Would you cut them some slack that you won't cut for yourself? Would you show them more kindness?
I need to look at who I am and what I do from an outside perspective - that's the only way I can get close to showing and accepting appreciation for myself. Maybe one day I'll find another way, but for now, self-appreciation isn't very easy.