The tests and challenges that come to a person from the Almighty are so concealed and subtle the person being tested usually does not feel what is happening to him is a test. If he is aware it is just a test, he would definitely be able to withstand the difficulties and rise to the challenge, but then the test would not be a real test. Therefore, tests are concealed in such a manner that a person thinks they are merely obstacles and nuisances. A person who withstands such tests is truly elevated.
Sources: Tehilas yoel, p.190;Rabbi Zelig Pliskin’s Gateway to Happiness, p.235