Margaret Thatcher
(To which a clever friend of mine retorted: Because you know you can do nothing the next day)
1. Accept that it's just not important to me and consciously abandon it (perhaps with a quick WONTFIX update/handling, if needed).
2. Accepting that it is important and I'm as likely to keep postponing it, roll up my sleeves and do it now.
3. Accepting that it is important, but now is not a good time to tackle it, postpone it, but try to set things up such that I won't postpone it again. This includes blocking off dedicated time in my calendar for the new time, making sure I have the tools/prerequisites I'd need then, and if possible figuring out a motivational hack to prevent myself from postponing it again.
It's still hard, and I'm constantly learning what works for me and what doesn't, but I like that I'm making these choices more mindfully.