I don't mean a particular person; what I mean is the various departments who work in your business.
The finance dept, I.T. marketing, operations, H.R. production etc. Some of them will be ally's some will be enemies!
Life is easy when you have friends in all those departments. In spite of most companies working in silos ( even fortresses sometimes!) when you understand what is happening in other sections of the business you will reduce your stress levels becuase others will want to support you and your daily challenges.
Guess what? You need to build relationships, i.e. go networking internally. get to know others and the chances are both departments become more sympathetic to each other.
Pick the department you have most trouble with and invite them in with a 'Let's have a cup of coffee to see how we can help your department make life easier?'
When you offer, genuinley, to help others they want to help you? It's human nature.
need some help with internal networking?
Have a look here