Pretty good drawings man

some of them are pretty good, some don't look right, and some need a little bit of work but thats mainly on small details. As for deciding if you should continue to draw, well thats totally up to you, if you draw something and like it, then it doesn't matter what your friends think, or what strangers think (unless they are letting you know how you could improve your skills, and you feel that their suggestions would help).
Here is my suggestion, it's up to you if you will follow it

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As you stated that these drawing are roughly 5 years old, I think you should have a go at doing some drawings now, and see where you skills are at. Once you have done 3 or 4 drawings (try and keep them in the DBZ style), compare them to your old work, and then look at the fine details and see how you have improved or what you can improve on (in the new drawings, if there is anything you notice).
But in the end, it's completely up to you to decide if you will continue to draw or not, personally I think you shouldn't give up, keep drawing, and keep improving your skills.