Is it a sin to feel aroused?

I am trying to discipline myself not to think of anything lustful because I no longer want to pleasure myself as part of my spiritual growth. However, some thoughts sneaks in and before I know it, I would feel aroused. It’s been easier to control my actions because I have been on this journey for months but I do feel like I am committing a sin for having a physical reaction 😔. I have tried to distract myself and even pray to God to strengthen me. I feel guilty and even though I’ve been disciplining myself for months, some days are harder and I do end up pleasuring myself to make the feeling stop. Any thoughts/advice?