It is easy to be coerced by those who are complementary about who you are and what you do, but really want you to support and augment their own work by your association with them.
You may even find yourself running after them, wanting to finish a promised task, helping them in the way you agreed, but find yourself being secondary to an event that is bolstering their ego. Your interruptions being a challenge to the situation where their ego is being fed.
In this instance it is wise to offer thanks and ask to be advised when the help you promised will be required. Asking them to contact you, rather than you running after them.
When you adopt this approach you will be free from your commitment without ever needing to deliver it. For you will never be contacted, because for them, it is too much like hard work to chase You!