The Gemara in Brachot (32b) says that Tefillah is one of 4 things that need constant strengthening. I think that tefillah is to be looked at as an art form. It takes constant work to perfect it.
In general, people have the wrong idea that something in ruchniut should have effects immediately. Whether they do a mitsvah or otherwise, they think that they should be rewarded (or otherwise) immediately. I have to say that after doing birkat cohanim every day, sometimes I feel unsure of the benefits. But I remind myself that the Ribbono Shel Olam answers us with what we need and when we need it. Hashem knows whats best for us and the best time to give it to us.