Learn to say, "No". If the vendor or partner has asked you to do something specific, or asks if your laboratory has the capacity to take on a new project and you know you are short-staffed and will not be able to accommodate them, say no.
An example might be a vendor who is asking for your laboratory to gather statistical data outside the realm of contractual obligations. This task has been approved by leadership but your laboratory does not have the staff to do so, say no.
When negotiating pricing, if you know the numbers are not adding up, such as not enough margin will be generated, say no.
It is always best, to be honest in these situations. If you cannot deliver on a promise, then just say no. This is also a part of good communication - the honest exchange of information.