Omg why is marshmallow fondant so annoying. I've been making my cake for over 6 years now and sometimes I make marshmallow fondant and it's perfect and other times it just totally screws me over

What issues are you running into?  I am thinking the problem could be the temperature/humidity level in your home that could lead to issues.

Yes, please give us a little more idea of the problem.

different brands of product maybe??

I can tell you, not all marshmallows are alike. I found that out. I buy a no name brand from a local store. I stick to that brand now, as I tried others and it was a disaster. 

I've used both store brands and name brand marshmallows and have had no particular troubles with the LMF recipe.

You were fortunate Sandra. I tired some name brand marshmallows, and my mmf was gooey.