Perhaps it is perception. Maybe because you were doing a love spell involving one's will, that subconsciously you knew you were doing something big, and that caused you to be nervous or shaky. I'm not here to say it was right or wrong, but doing anything (good or bad) with someone's will (without them knowing) is a big choice. This has happened to me before. I recommend working on meditation and working with your subconscious to practice drawing up energy and finding your "flow". And by flow, I mean how much energy to draw up to the point when you know your limit on being shaky or not. Even if you still would like to draw up a lot of energy, perhaps it would also help to specifically channel and direct that through a wand or athame. Sometimes using tools such as those can help you focus better. Trust me, you got this and can do this! It's all about you on your own path and finding what works and what doesn't work for you. Also, if you continue to feel shaky after ritual, it helps to eat or drink something to ground you. Another way to ground is to visualize all the excess energy you had from that ritual, and push it back into the earth. Hope some of these tips work for you! Good luck!