There is no magic bullet to be optimistic and happy 100% of the time, but I've found there are 3 things that help with my mood substantially.
Money is security and women want security for themselves and their offspring. Women aren't necessarily attracted to beta bux, but they are more than willing (at least initially) to trade sex for money or access to money.
If she is always slow to respond she isn't all that into you. If she is slow to respond some of the time she is probably busy doing other crap.
She wants comfort. She found some schmuck for that, so continue to bang away. You get all of the benefits (no strings sex) and he gets all of the downsides (having to spend money on her).
Death sucks, there is no way around it.