As someone who's felt both, I can say that this is absolutely not true. The things I've done and regretted have had real, lasting effects and the things I've regretted not doing are only hypothetical.
We regret things we did (some marriage that didn't work out and destroyed our lives, some business decision that was bad, drinking and partying when we should have been getting ahead instead now we're at an AA meeting, spending sprees that left us broke, getting that tribal tattoo in our forehead while drunk, and so on) all the time...
