Do you remember anything about the combination?
For example, many safes have a combination that is something like 3 turns right to (X), 2 turns left to (Y), 1 turn right to (Z). If you can remember that sequence then it might be worth a shot at guessing the combination. You can probably safely (no pun intended!) assume that there is a 1 or 2 number window to each side of the correct number that will work to open the safe, so you don't have to try every number, maybe just every 3rd number. I have a feeling that would still take you a few dozen years, but it's a start.
