maybe you're not wet enough. try lubrication. also, make sure you are in the mood and completely relaxed. you'd be surprised at how much your mindset has to do with it. i would just recommend relaxing and trying lube and encouraging foreplay to get yourself excited. good luck!

I'm not trying to sound rude in the least, but is he ridiculously small, size matters if it's incredibly small or big.

Also, maybe he's not frisky enough in bed for your liking?

And yes, the mind has the most control over the situation.