Completely normal. 
I don't know anyone who is seriously involved in any hobby that doesn't stress a little sometimes... Watch a classic car or motorcycle enthusiast try to get a stubborn engine running. If it's not occasionally challenging then I lose interest. The payoff is when you get something right and get to enjoy it. For me in this hobby that's breeding projects and aquascaping.
I don't know anyone who is seriously involved in any hobby that doesn't stress a little sometimes... Watch a classic car or motorcycle enthusiast try to get a stubborn engine running. If it's not occasionally challenging then I lose interest. The payoff is when you get something right and get to enjoy it. For me in this hobby that's breeding projects and aquascaping.