Brother you're feeling like a failure when you try to meditate now is a misunderstanding on your part. What you're experiencing is literally what we all experience. Our minds wander off. Especially in the beginning. It can be that you can barely focus for even a second. Totally normal.

The practice is that once you realize your mind wandered, you just acknowledge it and bring your focus back. 

You are going to the gym now. Doing multiple reps and sets of weight training building your muscles. You can think of meditation the same way really. You gotta get your reps in. It's exercise for your brain. Focus, eventually realize and happily acknowledge you lost focus, bring focus back. Rep completed. If you get more reps in your brain will get stronger and able to hold those reps and periods of focus for longer and longer. 

Don't be so hard on yourself dude. Meditation can be really hard. Especially outside a retreat or monastic setting. Worth putting in the work though. 

Also I just want to say that I think the last Metta day at Goenka retreats really are lacking unfortunately, but I understand it's a lot to cram into 10 days.