"I couldn't believe it. It seemed so improbable. She couldn't bear the sight of him. It was more than improbable; it was incredible. I thought it was merely jealousy. You see, I've always been jealous, but I trained myself never to show it; I was jealous of every man she knew; I was jealous of you. I knew she didn't love me as I loved her. That was only natural, wasn't it? But she allowed me to love her, and that was enough to make me happy. I forced myself to go out for hours together in order to leave them by themselves; I wanted to punish myself for suspicions which were unworthy of me; and when I came back I found they didn't want me -- not Strickland, he didn't care if I was there or not, but Blanche. She shuddered when I went to kiss her. When at last I was certain I didn't know what to do; I knew they'd only laugh at me if I made a scene. I thought if I held my tongue and pretended not to see, everything would come right. I made up my mind to get him away quietly, without quarrelling. Oh, if you only knew what I've suffered!"

Then he told me again of his asking Strickland to go. He chose his moment carefully, and tried to make his request sound casual; but he could not master the trembling of his voice; and he felt himself that into words that he wished to seem jovial and friendly there crept the bitterness of his jealousy. He had not expected Strickland to take him up on the spot and make his preparations to go there and then; above all, he had not expected his wife's decision to go with him. I saw that now he wished with all his heart that he had held his tongue. He preferred the anguish of jealousy to the anguish of separation.

请教老师：

上面节选中，出现的 leave them by themselves 究竟是什么意思呢？不懂by themselves什么意思？这里的them是指2个人还是指hours的复数呢？

顺便麻烦老师分析and he felt himself that into words that he wished to seem jovial and friendly there crept the bitterness of his jealousy，尤其是himself that 和 there 没看懂，不知道怎么分析。