A classic mistake that many people make on being promoted (whether internally or in a new firm) is failing to promote themselves. That does NOT mean setting up a campaign to tell your employer and colleagues just how wonderful you are, even if it happens to be true. It means internalising your promotion, and recognising that you are no longer doing the old job.
Yes it seems obvious. Yet the temptation for the lawyer who has just made partner by grinding through chargeable hours is to expect to be successful by doing more of the same. The new job might instead require much more emphasis on staff management, client management and so on. By continuing to act as they did in the old job, the lawyer sets themselves up to fail as a partner.
As a business executive once remarked, everybody is more comfortable doing the job one level below their own – that will come more easily, be less stressful, and be less open to criticism. But if you want the promotion, it is the new job that you have to do.