Can I decaffeinate tea myself?

YES. It is possible to prepare ordinary tea so as to remove most of the caffeine from the finished product. Caffeine is very water-soluble, more so than many of the flavour components in tea. So a very brief infusion can remove much of the caffeine while preserving flavor.

Here's how to do it: boil enough water for twice as many cups as you intend to drink. Pour the normal amount of water over the leaves, then infuse for twenty to thirty seconds. Pour off the resulting brew and discard, retaining the leaves. Bring the water to a boil again and pour it over the same leaves, this time infusing for the normal three to five minutes. This infusion should be caffeine free.