This is the only hard achievement of the game. The thing to remember is unlike most games of this type, there is NO penalty for running into yourself! So after you hit 70 or so in length you will notice the speed realty ramping up! No worries! If your about to hit the wall, simply hit the exact opposite way your running! You will double up onto yourself without penalty! Use this technique to stay alive at break neck speeds towards the 100 mark and also use the U-turn tin inch your way up to a just missed tail (if going left, hit in quick succession up right) to snag a tail you just missed rather than going for a whole new line / angle on it. Again, for tails up against a wall, carefully line up a shot and just pull the other direction as you get close. Repeat as needed till you get it. It's better to be too soon than to go splat! I cleared 100 tails before 20 deaths!