You need to excel in what you do to achieve your ambitions. Excel = perform exceptionally well. Sometimes you need to swallow your pride. No they don't really work. Especially sentence 1. Sentence 2 may work in some situations, for example swallowing your pride to work in a lower paid job rather than loose your home through debt. Example you have lost your job but you refuse to work as a labourer and you are in debt, but the only jobs available are labouring jobs, you have to swallow your pride, do the labouring job and pay the rent or loose your home.

To answer your follow up question "undermine yourself" means to make yourself less able and less effective, the sentence contradicts itself. If you are undermined you will be unable to achieve your ambitions, to get what you want. See my comment responding to your comment.

No, the first sentence doesn't make much sense. To undermine yourself would be a very strange thing to do and most likely would result in you failing to achieve what you want. The second sentence makes perfect sense, except that you missed out a word: "to achieve what *you* want".

I appreciate your comment. Thank you.

Hi, I don't think they have the same meaning as "undermine" the dictionary definition is: to gradually make someone or something less strong or effective: economic policies that threaten to undermine the health care system whereas swallow your pride means to humble yourself or to humiliate yourself.