I would base that decision on your profit margin. If you have a high profit margin, handling a few returns is not a big issue. If you have a low profit margin, returns can really be a hassle and cut into profits from the time spent dealing with them.
If you're aggressive but honest and not deceptive about your product and what it can do for your customer, I don't think you will have an inordinate number of returns as a result. Or, I would think you would not have an excessive number of returns.
I think that would depend on both the product and the client. If you give them a good deal, will they share that with others, or keep it to themselves as their own little secret?
And, if you have a product that's available from many places, you might just educate your prospect on the product and then they later forget about your site and end up buying elsewhere. Then, your competitor has you to thank for making their sale.
In such as case, you want to nurture and educate the customer about your product, but then to get them to buy "right now"!
You don't need to be too aggressive, and I would not be dishonestly aggressive, but you do want to try to get them to buy now without turning off people that don't like aggressive sales tactics.
Tough line to walk!
The nice thing about the web is that you can try different things and easily change them if they don't work. You could try a harder sell (just not too hard that it harms any reputation you may already have established). See how it works. Depending on your traffic, you may see the results in a few days or a couple months.
You may find, as I have, that your own preferred way to shop is not the most profitable. ;-)