Perception matters more than effort or talent
Nobody cares about your dedication, work ethics etc as long as you ensure that you maintain visibility. The person who “works” long hours, talks without having anything to say, has a “loud” extroverted persona has higher chances of being promoted.
Everyone is expendable
I have seen many people, whom I thought were indispensable, asked to let go. One failed initiative, an altercation with the boss, a year of under-performance is enough to undermine years of your contributions.
So don’t be complacent. If you are not evolving constantly to maintain your competitive edge, someone will catch up to you and make you redundant.
In the oldest versions, a lion threatens a mouse that wakes him from sleep. The mouse begs forgiveness and makes the point that such unworthy prey would bring the lion no honour. The lion then agrees and sets the mouse free. Later, the lion is netted by hunters. Hearing it roaring, the mouse remembers its clemency and frees it by gnawing through the ropes.
I have cordial relationships with everyone I need to interact with, even the ones I talk to sporadically. And I have received assistance and help every time I needed. A company is a huge machine and you can’t forever work as a silo. Be nice and polite to everyone, you never know who may save your ass one day.
Don’t be a Stark
If you trust everyone, are completely honorable (read: naive), you will get screwed over by everyone else.
Or a Lannister
Whilemight be an effective battle intimidation strategy, once you have burned all yours, you are stuck on your little island. People will just wait for you to “starve to death”. Don’t be the jerk. If your colleague/competition is one, don’t get cowed down either.