Heartbroken to find out that my local post office often misplaces post cards

I sent out around 10 cards within India only - none of them reached. I knew a few of them were bound to get lost, but I thought atleast 1 or 2 would be delivered.

Do you guys think putting it in an envelope and sealing it, would increase my success rate? I literally got into this hobby 1 month back, and I don't want to give up on it so easily.