I haven’t really thought about this topic before, but I believe that chance and skill are the main reasons some people get promoted. Whether or not you have the opportunity to be promoted often depends on luck. Chance is shaped by factors like time and place. If you have a good opportunity now, it’s possible that you wouldn’t have had the same chance if you were in a different situation or time period. However, even if you do get the opportunity for promotion, you won’t succeed without the necessary skills. You have to be able to seize the opportunity when it comes. (A few idioms you could also use here might be: 'seize the moment', 'strike while the iron is hot', or 'grab the bull by the horns'!) Taking advantage of opportunities is crucial not just for getting promoted, but in many areas of life. I want to be prepared for when a big opportunity comes my way. ('when opportunity knocks') This is all absolutely fine, I suggested a few idioms that could be useful here as well!