The word "ambition" comes with a variety of connotations.
>There are doers and there are talkers.
There are those who use their ambition to define a goal and then work tirelessly to achieve it. Think of the mountaineer who plans and trains for decades to eventually ascend Mt Everest.
Then there are those who share their ambition by talking about it. Seeking recognition, etc for "being ambitious". Staying with the mountaineer theme, those who refuse to climb a lesser mountain as not being important enough to expend their precious talents upon. It is these folks that if they somehow make enough money in some form, end up chartering a helicopter and sherpas to climb Mt Everest.
The word “ambition” is indeed vague, and this is unfortunate, as there is a rich vocabulary full of distinction we ought to be using. (You see the same thing when people use “passionate” as a virtue, such as in job postings when what they mean is “enthusiastic”. Taken literally, you certainly don’t want passionate employees!)
In the strict sense, ambition [0] is an inordinate love of honor.
Perseverance [1], OTOH, is the ability to endure suffering in pursuit of a good. Both effeminacy (refusal or inability to endure suffering to attain a good) and pertinacity (obstinate pursuit of something one should not) are opposed to perseverance.
It seems that ambition is therefore opposed to perseverance, since it can either be effeminate (the ineffectual daydreamer that makes big plans that he never realizes) or pertinacious (the person who bites off more than he can chew).
Prudence [3] involves the application of right reason to action, which itself presupposes right desire. An inordinate love of honor is therefore opposed to prudence, because it involves an inordinate desire. Furthermore, prudence presupposes humility [2], which involves knowing the actual limits of your strengths and qualities (it is not the denial of the strengths and qualities you actual have, which is opposed to humility and a common misconception!). Humility allows us to moderate our desires. In that sense, ambition as an inordinate desire for honors beyond one’s reach lacks humility.
[0] https://www.newadvent.org/cathen/01381d.htm
[1] https://www.newadvent.org/summa/3138.htm#article2
[2] https://www.newadvent.org/cathen/07543b.htm
[3] https://www.newadvent.org/cathen/12517b.htm