There is this issue among philosophers. Much like dietitians they are of the opinion that whatever you really like doing is bad for you. There must have been a serious design issue when they assembled humans. Or, perhaps, the issue is a minor glitch in the software that put a '0' wherever there should have been a '1'. Or, in emoticon terms, put a 'Thumbs up', or even a 'Heart', where it should have programed a 'Thumbs down'.
I mean, here you go around assuming that self-love is the best love. And then here pops up Tiru saying this.
Amaindhaang gozhugaan alavariyaan thannai viyandhaan viraindhu kedum - Tirukkural
He who fails to work in harmony with those around him, who knows not his own limitations and who indulges in self-admiration brings upon himself a swift destruction - Loose translation
And THAT is that. Admire yourself and you will soon be destroyed. Though, I suppose, that a lot has to be read between Tiru's lines. He was so pithy that you had to fill in a lot of the blanks all by yourself.
Which means that he really is not asking you to flagellate yourself. I mean, if you have really done something wonderful, he probably does not ask you to refrain from feeling proud about it. Nor does he expect you to tie yourself up in knots, modestly denying that you had anything to do with it. But, yes, just because you do not need to say, 'No, I did nothing much' does not mean that it will hurt for you to say, 'I could not have done it without the help of...'. See what I mean? It is always possible to say I-dun-it modestly!
But even that pride...it can be overdone. Keep talking about how wonderful you are, what you did that nobody else could do, and you can slip over from 'legitimate pride' territory to 'too full of himself' territory.
But THAT is not all that Tiru is saying. Admiring yourself is also not to admit that you can do any wrong. Which also means that you are never going to take any criticism well. And the next time you get pissed with someone never accepting his mistakes, always blaming someone else for whatever goes wrong and refusing to learn anything because he is already perfect...well, look into the mirror and think about how your boss feels about you!
IF you have that sorted, this business of not being blindly in love with yourself, it automatically means that you are open to understanding what your limitations are likely to be. AND a person who understands that he HAS limitations is well on his way to working in harmony with others.
ALAS! Even I am not allowed to admire myself!