My worst coding mistake

In my last project for the distributed application programming, I was working on encryption for messaging between two users, the mistake was after decrypting the message you should trim it, and I was trimming before which made the message corrupt, this mistake costed me 2 weeks of delay since I couldn't find the problem, the code was like this
Message=decrypt(message.trim());
Where it was supposed to be
Message=decrypt(message).trim();