Just think about it, if you keep locking yourself up in your room, there's no way you'll ever escape roneriness. If you want to do something about that, you have to go outside.
So, start from tomorrow. You'll probably feel bad about it, you'll want to postpone facing the world and rather just keep watching your animu and fapping. However, that person you're supposed to meet someday, that person you're meant to live your life happily with could be walking by. If you stay inside, you'll miss her for sure. In that case, the only thing to do is to brace yourself and go.
Wander aimlessly, enjoy your surroundings, do some shopping, whatever you feel like it. Don't feel too pressured, you won't find her on your first day anyway. Just relax and let things go on their own pace.
Do this every day. Sure, you're likely to keep being alone. But in time, that will stop bothering you. You'll start enjoying the outside world just for what it is, even if the person you were hoping for didn't show up. And, of course she didn't. After all, she died in a car accident 2 years ago.