The Microsoft Manual of Style for Technical Publications is quoted by Business Writing as suggesting:
Restructure the sentence so that the address is not at the end of
Set off the address, like this, with no period (full stop):
Please visit my website at:
However the same site also quotes the The Chicago Manual of Style as saying:
Other punctuation marks [other than the slash] used following a URL
will readily be perceived as belonging to the surrounding text. It is
therefore unnecessary to omit appropriate punctuation after the URL.
I would highly recommend choosing option 1 above to remove the problem completely and also consider removing the explicit request to follow the link from the sentence – so your example becomes for example:
Don’t worry, you can reset your password if you forget it.
It is not only a problem with copy/paste. If Thunderbird (among others) receives a plain text message with an URL, it will transform it to a clickable URL, including the end period, as it is valid in an URL. A number of other punctuation characters are also legal, so care must be used.
Tradition in such plain text messages is to surround the URL with < and > as kind of quotation marks (as the latter can be problematic too; depends on the algorithm of the URL detector):
You can see that in <http://example.com/foo>.
Otherwise, as said above, a little rewording can help while preserving the elegance of the sentence (sic):
You can see that in the http://example.com/foo page.
In this specific example, the period is not really necessary. What follows the full colon need not always be a word/ phrase or some linguistic construct. It could even be an icon/ image etc.
In general though, it is always preferable to place the link either inside the sentence or behind a part of text.
Please follow the link http://example.com/recover/TOKEN to reset your password.
To reset your password, please follow this link.
Reset your password
Please note the use of the period (and the comma).