First of all, stock prices are volatile. If you buy shares in a stock mutual fund, any stock mutual fund, your investment value will change every day. In a recession most fund shares will go down, day after day, week after week, month after month, until you are ready to tear your hair out, unless you've already gone bald from worry. It will insist on this even if Gandhi, Jefferson, John Lennon, Einstein, Merlin and Golda Meir all manage the thing.
Stock markets show remarkably little respect for people or their reputations.
Furthermore, if the fund has really been successful, you might be buying someone else's whopping gains when you invest, on which you may have to pay taxes for returns you didn't earn. Just try and find somewhere you don't, though. It goes with the territory. Live with it. If you can't do that, go bury your money in a jar or put it in the bank and don't bother us about why your investment goes south sometimes or why water runs downhill.