Sir,
0. Admit to yourself that you are lost, instead of trying to convince yourself you know where you are.
1. Do not continue any further.
2. Check heading and the time travelled from the last known waypoint.
3. If able, return to a place that you recognise and are able indentify without a doubt. (This should be fairly easy if you have OFP and you know how long you've come with a known heading)
4. If 3 doesn't work, use radio to get assistance from ATC and use nav aids to plot yourself onto the map again.
Happy landings sires,
Olabade