The more a person worries about what’s going to be and the more hishtadlus one does, the harder it is to get what you want.
The Gemorah in Eiruvin (13a) tells us, “The more a chases after stature, the more it runs away from him. The more a person runs away from stature, the more it chases him.” The Vilna Gaon z”l explains that this is true for any middah and desire, the more you pursue the harder it is to obtain.
Certainly this is true for bitachon. When you rely only on Hashem, what you desire comes to you in a much easier way. But when you chase it, you find that you are exerting a lot of effort while it still eludes you.