I also work well under deadlines but perform horribly without them. Upon reflection I realized a lot of my motivation is related to not disappointing others and/or embarrassing myself. Neglecting personal projects makes me feel like shit, but it's missing the public humiliation factor so it won't get me moving. A possible solution is to create deadlines for yourself and share them with people who will hold you accountable, or to whom you at least feel accountable. I also try to imagine how I will feel in a week, month, or year down the road when I still haven't done THE THING, and realize that it's only going to get worse the longer I go. This isn't 100% successful but it does work sometimes.

This isn't that rare. It is half the reason people hire personal trainers. The military also uses this technique, by framing failures as letting down your comrades rather than yourself.

This is a tricky thing to balance because using negativity and self criticism can become destructive. My grandma used to have a coal burning stove for heat. She said it was awful because too little coal and it would go out and was really hard to re-light. But too much coal and it would explode and blow coal dust all over their little house. I feel like self hate is kind of like that oven. Unfortunately nothing else has ever truly worked for me.

Also, I should add, one thought that brought me some self-forgiveness was the evolutionary roots of laziness. If you think about it, as an organism, if you're well fed and in a good location your best bet is to chill under a shade tree until something comes up. As humans we are kind of cursed with extra simulation cores in our brain that can constantly iterate every single permutation of the future, and that leads to anxiety, but laziness is actually a virtue from an evolutionary perspective. So cut yourself some slack now and then.