Whilst @EEAA's point about Windows 8 not being a server is entirely valid there are some bits of hackery that may help?
First of all I am assuming that you are concerned with ensuring that the RRAS service is running, in which case you have a couple of options.
Your first is to query your event logs and locate why the service is stopping, resolve that issue and you will be away (haven't got enough information to even begin to help with that )
Second option is to open the Services panel (Start > run > Services.msc), locate the RRAS service and edit its properties, select the 'Recovery' tab, and set to to restart on all your options there. This should keep it available although if you have a regularly failing service you may find that this becomes just a constant sequence of fail > restart and leaves you with no service anyway.
A third option thats worked for me is to use a separate script to monitor the service status and start it if its anything but running. In powershell
IF((Get-Service RemoteAccess).status -ne 'Running'){Restart-Service RemoteAccess)
Schedule that to run every 15 minutes, or wrap it in a DO...WHILE loop and that'll keep your service running.