Others have posted longer term solutions (bigger cup, skill issue, etc). In the immediate situation you have some options:

1. Decant to another cup. There’s no way to do this without creating a mess.
2. Put a plate under the mug and carry it back to the desk with a couple of paper towels to clean up the mess (of work is urgent)
3. Leave it on the counter and sit there for 5 min till the top can be sipped before going back to the desk (if work can wait)