I'm not going to toss out some trite motivational bullshit. No one can motivate you from the outside, you have to find that yourself.

This is a great first step but that's all it is, a first step. There are a shitload of steps between here and the end, which is the day you die. The more of those steps you take, the farther out that day gets. Own your situation. You ate yourself to 400lbs. It happened but, unlike most things that happened, you have the power to undo it.

There will be days you want to say fuck it and give up. Those days are the days you need to remember exactly why you started. They're also the most important days for you to keep going.

The up side is that, at your size, almost any change at all will kick off weight loss for a little while. You have to fix your diet first but even that change can be one small change at a time. I don't know your eating habits but a good typical starting point is to stop drinking calories. Eat more green vegetables. Cut back on refined carbohydrates and choose more high quality, lean protein sources. Counting calories isn't important right now, you just need to get used to better overall habits. Don't even worry that much about exercise right now. Walk a little when you can but don't push the limits of your joints. If you can find one, get an under-desk bike or something that's relatively low impact.

I won't lie, this whole process sucks sometimes. It's not fun and there's There aren't shortcuts and it's something you'll have to do to differing degrees for the rest of your life. But the tradeoff there is you get to have more of that life.