Although work has your attention today someone special with pull you also, be firm and fair.
Work has the bulk of your attention right now and this could be tricky when someone special also wants your time and attention today. If it's that this person needs you for something important you will have to make time for them and be supportive. But if it's just a whim you will have to be firm and explain to them how busy you are and that you will spend time with them later.