Not flaming you, etc but..
The program was called MD5 cacker, it uses dictionary attacks,
It means your password exists in the dictionary!
Then the weakness is on your poor choice of words. A good security practice is to not using dictionary words as your password. You can still use some variation of dictionary words (i.e. CapItaLizAtiOn, numb3rl3tt3r5, verylongpassphrase, etc.). While this is not fool proof, a basic dictionary attack will not get your MD5 easily. The cracking program will have to brute force through it for every letter in the word in the phrase.
Also, MD5 Cracker is actually not reversing your MD5 code into cleartext, but guessing cleartext and convert it to MD5, hoping it will match with yours.
Hopefully this will ease your (and everyone's) mind a bit.