Firstly, kudos to your decision of switching to a fully plant-based diet. I feel that you might have to follow some strategies to make the transition easier. I would suggest following an approach that involves starting slow, plus reducing processed food and meat intake. At the start, try to have the plant-based food items that you always enjoy, like oatmeal, jacket potato, vegetable stir-fry, lentil stew, or pasta primavera. After that, build on these meals gradually.
 
It is advisable to not pressurize yourself to achieve perfection suddenly. Try to view the transition to a plant-based diet as a slow and steady process. Remember that any sort of transition usually takes time to achieve. Much of the process is about experimenting to discover what does not work for you and what does. Wish you all the best on your endeavor of becoming a vegan.