Every time you say "I can't I'm too busy" to someone or something, add on "it's just not a priority." This tactic was inspired by a podcast I listened to with Debbie Millman, designer, and podcaster among many other things.
So, if your child comes to you and asks you to play with him. You can reply "I can't son, I'm too busy and you're just not a priority right now."
When you think about going to the gym for your health say "I'm too busy and my health is just not a priority."
If you really want to start a company but come home after a long day at the office just say "I'm too busy and starting my own company is just not a priority."
When your friends ask you why you haven't gone to visit your parents this year you can say "I'm too busy and they are not a priority."
You make time for things that are a priority. Choosing not to is your choice and it's just because it wasn't a priority.
By doing this you can either accept that the thing you thought you wanted just isn't a priority so you can stop agonizing over it. Just accept that your child, health, parents or dreams are not priorities for you right now. It may honestly be the case.
Or, you may believe that is just not the case and they actually are priorities. Then anything you say to justify your choice of "being busy" is just an excuse. Now you can focus on making time instead.