Honesty and kindness have nothing to do with "doing better" one way or the other. So you may as well be honest and kind and at least not mess with anybody else's day.
You don't do those things to get a reward. That's Christian nonsense. There's no god to give you treats for not being an asshole.
It's still better to not be an asshole, though. It feels nice, and there's no advantage to assholeyness, either. I'd be slightly worried about having the tendency to think that assholes being successful means you get successful by being an asshole. Not only are you just as likely to fail (probably a bit more, becasue nobody likes an asshole, so it's harder to get people to help you or be nice to you), but then you'd be an asshole and have to deal with the emotional fallout from that.
In all seriousness, plenty of people out there justify their own self-centered tendencies with this exact train of thought. It's broken and bad and demontrably not true. Don't be an asshole. And that includes both to stop expecting a cosmic reward for being nice and to stop thinking that being nice precludes you from having to find effective, ethical strategies to get what you need or want.
That make sense? I think it makes sense.