I have been thinking about this a lot lately: why do people choose to say yes or no to a request for help, time and support? While there are certainly people who are going to take and never give, they are rare (thank goodness!). I believe that most of the time individuals want to comply with our requests, but we make it too hard for them.
My suggestion (to you and myself) is this: Ask for things that are super simple and straightforward for the other person to do and where a yes is easy.
This takes practice, so start today.