I'm at the start of the "one man army" thing at the company I started working at last month, thanks for being so candid about your experience. I'm gonna really be forceful to make sure we can hire new people for backup. Last night I worked until 8PM. That was the first time, but I suspect it won't be the last unless I really take action on finding someone to help.
Please be very careful, this is how it started for me, too.
At first it's fine, you have the feeling that you're building something up from the ground and that you really make a change. While that might be true, it is very easy to get smashed by your construction later on.
Please don't let that happen and get yourself a colleague as soon as possible.
