Let’s look at POV shifts within paragraphs and some possible solutions:

Version 1:  

Julia smiled to  herself at happy memories of children tumbling amongst the fallen leaves in autumns long past. Now the only thing tumbling about in the garden was her husband, Simon. He vigorously rubbed the grit from his eyes with his hands, having accidentally hit himself in the face with the grubby roots of a particularly stubborn dandelion.

Julia’s cat stared at Simon curiously with her bright green eyes from the edge of the flowerbed. She wondered what he was doing and hoped that all that strange pulling and tugging on his part might be the prelude to a tasty morsel or perhaps an interesting game. Realising it was neither, she gave a loud yawn and stretched herself to her full length, before sauntering back in the direction of the house.

In the living room, Julia laughed. Poor Simon, she thought, even Puss thinks he’s boring.

Simon groaned. He hated this place. 

Version 2: 

Julia smiled to herself at happy memories of children tumbling amongst the fallen leaves in autumns long past. Now the only thing tumbling about in the garden was her husband, Simon.

Simon rubbed the grit from his eyes, having accidentally hit himself in the face with the grubby roots of a particularly stubborn dandelion. The pair of green feline eyes gazing curiously at him from the edge of flowerbed unnerved him. That cat – Julia’s cat – didn’t like him, he was sure of that. As if to prove his point, the animal gave a sudden loud yawn, stretched herself to her full length and sauntered in the direction of the house. Simon groaned. He hated this place.

Watching from the living room, Julia laughed. Poor Simon, she thought, even Puss thinks he’s boring.

Commentary: 

• In Version 1, the POV shift from Julia’s point of view to Simon’s is unnerving. One sentence on, we get a further shift: we are now viewing Simon from the cat’s POV. Then we are back to Julia, then Simon again. The end result is confusion and irritation for the reader as they try to figure out on exactly who or what they should they be focussing, no doubt also asking themselves at the same time why they are having to work so hard.

• In Version 2, the shift from Julia’s POV is more clearly signposted (although still a little disconcerting). We’ve also lost Puss’s POV. This may be quirky, but it is distracting and makes the cat more significant than is warranted in the overall scheme of things. In addition, we are setting up reader expectations only to cruelly dash them, if this is the only instance of her POV. Cutting her out allows us to focus more clearly on Simon’s feelings, which is more useful for the story, and gives the reader a better sense of his and Julia’s relationship and the physical and emotional distance between them.

Whose story is it anyway? 

Of course, all of the above assumes that Julia and Simon are the two viewpoint characters in the story, but the tale could just as well be told solely from Julia’s POV or Simon’s POV, or indeed, entirely from Puss’s POV. Or you could use the cat yawning at Simon as the pivotal event in which the same story is told from three different points of view. To be honest, the possibilities are endless and the joy of being a writer is you get to try out as many as you wish. So, please, go explore and enjoy!