If you've forgotten your Subversion password, you should be able to retrieve it from another machine where you've succesfully made a commit before.
If you look in the local cache for your server's authentication type, you should see a series a files with hexadecimal names.
For example, for a server using simple or basic authentication:
$ ls ~/.subversion/auth/svn.simple 2af94d688c4073220b0a6af1b5884861 887652dff29c33e3f09394ea7379fac9
If you then look in one of the file, you should see your password:
$ cat ~/.subversion/auth/svn.simple/2af94d688c4073220b0a6af1b5884861 | grep -A 2 password password V 9 mypassword
The above commands and locations are for a Linux box, but something similar should work on other OSes.