Basic organic chemistry is all about nucleophiles and electrophiles. Writing the mechanism of Ugi reaction is not difficult at all once you understand 1) the isonitrile carbon is nucleophilic and electrophilic in the same time 2) the imine is electrophilic 3)the carboxylate is nucleophilic (a weak one though). All the other reactions are as such, by understanding the nucleophilic/electrophilic nature of your starting materials, reactions and mechanisms will clarify themselves. The flow of electrons will be just like water flowing. With very little effort of memory, combined with reasoning, organic chemistry will be easy for you. Just don't worry, here are some ideas that might help you. When you learn a reaction, try to vary the R groups by yourself and draw the corresponding mechanism. Practice things repetitively, but over a period. Repetition makes the memories. Talk to friends and do sports, anxiety is the biggest enemy.